diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/InternalAggregation.java b/core/src/main/java/org/elasticsearch/search/aggregations/InternalAggregation.java
index 563a958109b..4fb6a434c84 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/InternalAggregation.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/InternalAggregation.java
@@ -185,7 +185,7 @@ public abstract class InternalAggregation implements Aggregation, ToXContent, Na
             builder.startObject(getName());
         }
         if (this.metaData != null) {
-            builder.field(CommonFields.META);
+            builder.field(CommonFields.META.getPreferredName());
             builder.map(this.metaData);
         }
         doXContentBody(builder, params);
@@ -240,18 +240,17 @@ public abstract class InternalAggregation implements Aggregation, ToXContent, Na
      * Common xcontent fields that are shared among addAggregation
      */
     public static final class CommonFields extends ParseField.CommonFields {
-        // todo convert these to ParseField
-        public static final String META = "meta";
-        public static final String BUCKETS = "buckets";
-        public static final String VALUE = "value";
-        public static final String VALUES = "values";
-        public static final String VALUE_AS_STRING = "value_as_string";
-        public static final String DOC_COUNT = "doc_count";
-        public static final String KEY = "key";
-        public static final String KEY_AS_STRING = "key_as_string";
-        public static final String FROM = "from";
-        public static final String FROM_AS_STRING = "from_as_string";
-        public static final String TO = "to";
-        public static final String TO_AS_STRING = "to_as_string";
+        public static final ParseField META = new ParseField("meta");
+        public static final ParseField BUCKETS = new ParseField("buckets");
+        public static final ParseField VALUE = new ParseField("value");
+        public static final ParseField VALUES = new ParseField("values");
+        public static final ParseField VALUE_AS_STRING = new ParseField("value_as_string");
+        public static final ParseField DOC_COUNT = new ParseField("doc_count");
+        public static final ParseField KEY = new ParseField("key");
+        public static final ParseField KEY_AS_STRING = new ParseField("key_as_string");
+        public static final ParseField FROM = new ParseField("from");
+        public static final ParseField FROM_AS_STRING = new ParseField("from_as_string");
+        public static final ParseField TO = new ParseField("to");
+        public static final ParseField TO_AS_STRING = new ParseField("to_as_string");
     }
 }
diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/InternalSingleBucketAggregation.java b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/InternalSingleBucketAggregation.java
index 7ce66e4ae44..490c7a36878 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/InternalSingleBucketAggregation.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/InternalSingleBucketAggregation.java
@@ -131,7 +131,7 @@ public abstract class InternalSingleBucketAggregation extends InternalAggregatio
 
     @Override
     public XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
-        builder.field(CommonFields.DOC_COUNT, docCount);
+        builder.field(CommonFields.DOC_COUNT.getPreferredName(), docCount);
         aggregations.toXContentInternal(builder, params);
         return builder;
     }
diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/adjacency/InternalAdjacencyMatrix.java b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/adjacency/InternalAdjacencyMatrix.java
index 3a7dc284ab9..3d0839b7fb4 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/adjacency/InternalAdjacencyMatrix.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/adjacency/InternalAdjacencyMatrix.java
@@ -105,8 +105,8 @@ public class InternalAdjacencyMatrix
         @Override
         public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
             builder.startObject();
-            builder.field(CommonFields.KEY, key);
-            builder.field(CommonFields.DOC_COUNT, docCount);
+            builder.field(CommonFields.KEY.getPreferredName(), key);
+            builder.field(CommonFields.DOC_COUNT.getPreferredName(), docCount);
             aggregations.toXContentInternal(builder, params);
             builder.endObject();
             return builder;
@@ -207,7 +207,7 @@ public class InternalAdjacencyMatrix
 
     @Override
     public XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
-        builder.startArray(CommonFields.BUCKETS);
+        builder.startArray(CommonFields.BUCKETS.getPreferredName());
         for (InternalBucket bucket : buckets) {
             bucket.toXContent(builder, params);
         }
diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/filters/InternalFilters.java b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/filters/InternalFilters.java
index bd33f1608bc..51531222725 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/filters/InternalFilters.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/filters/InternalFilters.java
@@ -108,7 +108,7 @@ public class InternalFilters extends InternalMultiBucketAggregation<InternalFilt
             } else {
                 builder.startObject();
             }
-            builder.field(CommonFields.DOC_COUNT, docCount);
+            builder.field(CommonFields.DOC_COUNT.getPreferredName(), docCount);
             aggregations.toXContentInternal(builder, params);
             builder.endObject();
             return builder;
@@ -210,9 +210,9 @@ public class InternalFilters extends InternalMultiBucketAggregation<InternalFilt
     @Override
     public XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
         if (keyed) {
-            builder.startObject(CommonFields.BUCKETS);
+            builder.startObject(CommonFields.BUCKETS.getPreferredName());
         } else {
-            builder.startArray(CommonFields.BUCKETS);
+            builder.startArray(CommonFields.BUCKETS.getPreferredName());
         }
         for (InternalBucket bucket : buckets) {
             bucket.toXContent(builder, params);
diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/geogrid/InternalGeoHashGrid.java b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/geogrid/InternalGeoHashGrid.java
index b23faeba339..c1a6ad8be9a 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/geogrid/InternalGeoHashGrid.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/geogrid/InternalGeoHashGrid.java
@@ -120,8 +120,8 @@ public class InternalGeoHashGrid extends InternalMultiBucketAggregation<Internal
         @Override
         public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
             builder.startObject();
-            builder.field(CommonFields.KEY, getKeyAsString());
-            builder.field(CommonFields.DOC_COUNT, docCount);
+            builder.field(CommonFields.KEY.getPreferredName(), getKeyAsString());
+            builder.field(CommonFields.DOC_COUNT.getPreferredName(), docCount);
             aggregations.toXContentInternal(builder, params);
             builder.endObject();
             return builder;
@@ -223,7 +223,7 @@ public class InternalGeoHashGrid extends InternalMultiBucketAggregation<Internal
 
     @Override
     public XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
-        builder.startArray(CommonFields.BUCKETS);
+        builder.startArray(CommonFields.BUCKETS.getPreferredName());
         for (Bucket bucket : buckets) {
             bucket.toXContent(builder, params);
         }
diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/histogram/InternalDateHistogram.java b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/histogram/InternalDateHistogram.java
index 19e5dc1ec89..9815fdd2144 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/histogram/InternalDateHistogram.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/histogram/InternalDateHistogram.java
@@ -142,10 +142,10 @@ public final class InternalDateHistogram extends InternalMultiBucketAggregation<
                 builder.startObject();
             }
             if (format != DocValueFormat.RAW) {
-                builder.field(CommonFields.KEY_AS_STRING, keyAsString);
+                builder.field(CommonFields.KEY_AS_STRING.getPreferredName(), keyAsString);
             }
-            builder.field(CommonFields.KEY, key);
-            builder.field(CommonFields.DOC_COUNT, docCount);
+            builder.field(CommonFields.KEY.getPreferredName(), key);
+            builder.field(CommonFields.DOC_COUNT.getPreferredName(), docCount);
             aggregations.toXContentInternal(builder, params);
             builder.endObject();
             return builder;
@@ -437,9 +437,9 @@ public final class InternalDateHistogram extends InternalMultiBucketAggregation<
     @Override
     public XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
         if (keyed) {
-            builder.startObject(CommonFields.BUCKETS);
+            builder.startObject(CommonFields.BUCKETS.getPreferredName());
         } else {
-            builder.startArray(CommonFields.BUCKETS);
+            builder.startArray(CommonFields.BUCKETS.getPreferredName());
         }
         for (Bucket bucket : buckets) {
             bucket.toXContent(builder, params);
diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/histogram/InternalHistogram.java b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/histogram/InternalHistogram.java
index e6e23d3a615..046551fc58a 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/histogram/InternalHistogram.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/histogram/InternalHistogram.java
@@ -138,10 +138,10 @@ public final class InternalHistogram extends InternalMultiBucketAggregation<Inte
                 builder.startObject();
             }
             if (format != DocValueFormat.RAW) {
-                builder.field(CommonFields.KEY_AS_STRING, keyAsString);
+                builder.field(CommonFields.KEY_AS_STRING.getPreferredName(), keyAsString);
             }
-            builder.field(CommonFields.KEY, key);
-            builder.field(CommonFields.DOC_COUNT, docCount);
+            builder.field(CommonFields.KEY.getPreferredName(), key);
+            builder.field(CommonFields.DOC_COUNT.getPreferredName(), docCount);
             aggregations.toXContentInternal(builder, params);
             builder.endObject();
             return builder;
@@ -421,9 +421,9 @@ public final class InternalHistogram extends InternalMultiBucketAggregation<Inte
     @Override
     public XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
         if (keyed) {
-            builder.startObject(CommonFields.BUCKETS);
+            builder.startObject(CommonFields.BUCKETS.getPreferredName());
         } else {
-            builder.startArray(CommonFields.BUCKETS);
+            builder.startArray(CommonFields.BUCKETS.getPreferredName());
         }
         for (Bucket bucket : buckets) {
             bucket.toXContent(builder, params);
diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/range/InternalBinaryRange.java b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/range/InternalBinaryRange.java
index bb31d9a2480..ea515863363 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/range/InternalBinaryRange.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/range/InternalBinaryRange.java
@@ -133,16 +133,16 @@ public final class InternalBinaryRange
             } else {
                 builder.startObject();
                 if (key != null) {
-                    builder.field(CommonFields.KEY, key);
+                    builder.field(CommonFields.KEY.getPreferredName(), key);
                 }
             }
             if (from != null) {
-                builder.field(CommonFields.FROM, getFrom());
+                builder.field(CommonFields.FROM.getPreferredName(), getFrom());
             }
             if (to != null) {
-                builder.field(CommonFields.TO, getTo());
+                builder.field(CommonFields.TO.getPreferredName(), getTo());
             }
-            builder.field(CommonFields.DOC_COUNT, docCount);
+            builder.field(CommonFields.DOC_COUNT.getPreferredName(), docCount);
             aggregations.toXContentInternal(builder, params);
             builder.endObject();
             return builder;
@@ -270,9 +270,9 @@ public final class InternalBinaryRange
     public XContentBuilder doXContentBody(XContentBuilder builder,
             Params params) throws IOException {
         if (keyed) {
-            builder.startObject(CommonFields.BUCKETS);
+            builder.startObject(CommonFields.BUCKETS.getPreferredName());
         } else {
-            builder.startArray(CommonFields.BUCKETS);
+            builder.startArray(CommonFields.BUCKETS.getPreferredName());
         }
         for (Bucket range : buckets) {
             range.toXContent(builder, params);
diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/range/InternalRange.java b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/range/InternalRange.java
index a2228b7a27a..3d0cf1b5a8c 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/range/InternalRange.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/range/InternalRange.java
@@ -141,21 +141,21 @@ public class InternalRange<B extends InternalRange.Bucket, R extends InternalRan
                 builder.startObject(key);
             } else {
                 builder.startObject();
-                builder.field(CommonFields.KEY, key);
+                builder.field(CommonFields.KEY.getPreferredName(), key);
             }
             if (!Double.isInfinite(from)) {
-                builder.field(CommonFields.FROM, from);
+                builder.field(CommonFields.FROM.getPreferredName(), from);
                 if (format != DocValueFormat.RAW) {
-                    builder.field(CommonFields.FROM_AS_STRING, format.format(from));
+                    builder.field(CommonFields.FROM_AS_STRING.getPreferredName(), format.format(from));
                 }
             }
             if (!Double.isInfinite(to)) {
-                builder.field(CommonFields.TO, to);
+                builder.field(CommonFields.TO.getPreferredName(), to);
                 if (format != DocValueFormat.RAW) {
-                    builder.field(CommonFields.TO_AS_STRING, format.format(to));
+                    builder.field(CommonFields.TO_AS_STRING.getPreferredName(), format.format(to));
                 }
             }
-            builder.field(CommonFields.DOC_COUNT, docCount);
+            builder.field(CommonFields.DOC_COUNT.getPreferredName(), docCount);
             aggregations.toXContentInternal(builder, params);
             builder.endObject();
             return builder;
@@ -302,9 +302,9 @@ public class InternalRange<B extends InternalRange.Bucket, R extends InternalRan
     @Override
     public XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
         if (keyed) {
-            builder.startObject(CommonFields.BUCKETS);
+            builder.startObject(CommonFields.BUCKETS.getPreferredName());
         } else {
-            builder.startArray(CommonFields.BUCKETS);
+            builder.startArray(CommonFields.BUCKETS.getPreferredName());
         }
         for (B range : ranges) {
             range.toXContent(builder, params);
diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/sampler/UnmappedSampler.java b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/sampler/UnmappedSampler.java
index 6eb78c31c5c..5cabb618b8a 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/sampler/UnmappedSampler.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/sampler/UnmappedSampler.java
@@ -59,7 +59,7 @@ public class UnmappedSampler extends InternalSampler {
 
     @Override
     public XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
-        builder.field(InternalAggregation.CommonFields.DOC_COUNT, 0);
+        builder.field(InternalAggregation.CommonFields.DOC_COUNT.getPreferredName(), 0);
         return builder;
     }
 
diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/significant/SignificantLongTerms.java b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/significant/SignificantLongTerms.java
index ff2ea5b045b..6a714a6b035 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/significant/SignificantLongTerms.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/significant/SignificantLongTerms.java
@@ -99,11 +99,11 @@ public class SignificantLongTerms extends InternalMappedSignificantTerms<Signifi
         @Override
         public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
             builder.startObject();
-            builder.field(CommonFields.KEY, term);
+            builder.field(CommonFields.KEY.getPreferredName(), term);
             if (format != DocValueFormat.RAW) {
-                builder.field(CommonFields.KEY_AS_STRING, format.format(term));
+                builder.field(CommonFields.KEY_AS_STRING.getPreferredName(), format.format(term));
             }
-            builder.field(CommonFields.DOC_COUNT, getDocCount());
+            builder.field(CommonFields.DOC_COUNT.getPreferredName(), getDocCount());
             builder.field("score", score);
             builder.field("bg_count", supersetDf);
             aggregations.toXContentInternal(builder, params);
@@ -162,7 +162,7 @@ public class SignificantLongTerms extends InternalMappedSignificantTerms<Signifi
     @Override
     public XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
         builder.field("doc_count", subsetSize);
-        builder.startArray(CommonFields.BUCKETS);
+        builder.startArray(CommonFields.BUCKETS.getPreferredName());
         for (Bucket bucket : buckets) {
             bucket.toXContent(builder, params);
         }
diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/significant/SignificantStringTerms.java b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/significant/SignificantStringTerms.java
index b2c1f9ce1b0..d62213bc47a 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/significant/SignificantStringTerms.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/significant/SignificantStringTerms.java
@@ -104,8 +104,8 @@ public class SignificantStringTerms extends InternalMappedSignificantTerms<Signi
         @Override
         public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
             builder.startObject();
-            builder.field(CommonFields.KEY, getKeyAsString());
-            builder.field(CommonFields.DOC_COUNT, getDocCount());
+            builder.field(CommonFields.KEY.getPreferredName(), getKeyAsString());
+            builder.field(CommonFields.DOC_COUNT.getPreferredName(), getDocCount());
             builder.field("score", score);
             builder.field("bg_count", supersetDf);
             aggregations.toXContentInternal(builder, params);
@@ -164,7 +164,7 @@ public class SignificantStringTerms extends InternalMappedSignificantTerms<Signi
     @Override
     public XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
         builder.field("doc_count", subsetSize);
-        builder.startArray(CommonFields.BUCKETS);
+        builder.startArray(CommonFields.BUCKETS.getPreferredName());
         for (Bucket bucket : buckets) {
             //There is a condition (presumably when only one shard has a bucket?) where reduce is not called
             // and I end up with buckets that contravene the user's min_doc_count criteria in my reducer
diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/significant/UnmappedSignificantTerms.java b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/significant/UnmappedSignificantTerms.java
index 0823e0fb985..f9d8375af8c 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/significant/UnmappedSignificantTerms.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/significant/UnmappedSignificantTerms.java
@@ -107,7 +107,7 @@ public class UnmappedSignificantTerms extends InternalSignificantTerms<UnmappedS
 
     @Override
     public XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
-        builder.startArray(CommonFields.BUCKETS).endArray();
+        builder.startArray(CommonFields.BUCKETS.getPreferredName()).endArray();
         return builder;
     }
 
diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/DoubleTerms.java b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/DoubleTerms.java
index 09787ab9d09..ae18cb59d95 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/DoubleTerms.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/DoubleTerms.java
@@ -87,9 +87,9 @@ public class DoubleTerms extends InternalMappedTerms<DoubleTerms, DoubleTerms.Bu
 
         @Override
         protected final XContentBuilder keyToXContent(XContentBuilder builder) throws IOException {
-            builder.field(CommonFields.KEY, term);
+            builder.field(CommonFields.KEY.getPreferredName(), term);
             if (format != DocValueFormat.RAW) {
-                builder.field(CommonFields.KEY_AS_STRING, format.format(term));
+                builder.field(CommonFields.KEY_AS_STRING.getPreferredName(), format.format(term));
             }
             return builder;
         }
diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/InternalTerms.java b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/InternalTerms.java
index c09db32b27e..0fb4ceea33a 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/InternalTerms.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/InternalTerms.java
@@ -18,6 +18,7 @@
  */
 package org.elasticsearch.search.aggregations.bucket.terms;
 
+import org.elasticsearch.common.ParseField;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.xcontent.ToXContent;
@@ -44,10 +45,11 @@ import static java.util.Collections.unmodifiableList;
 public abstract class InternalTerms<A extends InternalTerms<A, B>, B extends InternalTerms.Bucket<B>>
         extends InternalMultiBucketAggregation<A, B> implements Terms, ToXContent {
 
-    protected static final String DOC_COUNT_ERROR_UPPER_BOUND_FIELD_NAME = "doc_count_error_upper_bound";
-    protected static final String SUM_OF_OTHER_DOC_COUNTS = "sum_other_doc_count";
+    protected static final ParseField DOC_COUNT_ERROR_UPPER_BOUND_FIELD_NAME = new ParseField("doc_count_error_upper_bound");
+    protected static final ParseField SUM_OF_OTHER_DOC_COUNTS = new ParseField("sum_other_doc_count");
 
     public abstract static class Bucket<B extends Bucket<B>> extends Terms.Bucket {
+
         /**
          * Reads a bucket. Should be a constructor reference.
          */
@@ -146,9 +148,9 @@ public abstract class InternalTerms<A extends InternalTerms<A, B>, B extends Int
         public final XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
             builder.startObject();
             keyToXContent(builder);
-            builder.field(CommonFields.DOC_COUNT, getDocCount());
+            builder.field(CommonFields.DOC_COUNT.getPreferredName(), getDocCount());
             if (showDocCountError) {
-                builder.field(InternalTerms.DOC_COUNT_ERROR_UPPER_BOUND_FIELD_NAME, getDocCountError());
+                builder.field(InternalTerms.DOC_COUNT_ERROR_UPPER_BOUND_FIELD_NAME.getPreferredName(), getDocCountError());
             }
             aggregations.toXContentInternal(builder, params);
             builder.endObject();
@@ -338,9 +340,9 @@ public abstract class InternalTerms<A extends InternalTerms<A, B>, B extends Int
 
     protected static XContentBuilder doXContentCommon(XContentBuilder builder, Params params,
                                                long docCountError, long otherDocCount, List<? extends Bucket> buckets) throws IOException {
-        builder.field(DOC_COUNT_ERROR_UPPER_BOUND_FIELD_NAME, docCountError);
-        builder.field(SUM_OF_OTHER_DOC_COUNTS, otherDocCount);
-        builder.startArray(CommonFields.BUCKETS);
+        builder.field(DOC_COUNT_ERROR_UPPER_BOUND_FIELD_NAME.getPreferredName(), docCountError);
+        builder.field(SUM_OF_OTHER_DOC_COUNTS.getPreferredName(), otherDocCount);
+        builder.startArray(CommonFields.BUCKETS.getPreferredName());
         for (Bucket bucket : buckets) {
             bucket.toXContent(builder, params);
         }
diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/LongTerms.java b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/LongTerms.java
index 8910f649d7d..98aa4825ee7 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/LongTerms.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/LongTerms.java
@@ -87,9 +87,9 @@ public class LongTerms extends InternalMappedTerms<LongTerms, LongTerms.Bucket>
 
         @Override
         protected final XContentBuilder keyToXContent(XContentBuilder builder) throws IOException {
-            builder.field(CommonFields.KEY, term);
+            builder.field(CommonFields.KEY.getPreferredName(), term);
             if (format != DocValueFormat.RAW) {
-                builder.field(CommonFields.KEY_AS_STRING, format.format(term));
+                builder.field(CommonFields.KEY_AS_STRING.getPreferredName(), format.format(term));
             }
             return builder;
         }
diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/StringTerms.java b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/StringTerms.java
index 8e3021dd170..b48c443fac9 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/StringTerms.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/StringTerms.java
@@ -86,7 +86,7 @@ public class StringTerms extends InternalMappedTerms<StringTerms, StringTerms.Bu
 
         @Override
         protected final XContentBuilder keyToXContent(XContentBuilder builder) throws IOException {
-            return builder.field(CommonFields.KEY, getKeyAsString());
+            return builder.field(CommonFields.KEY.getPreferredName(), getKeyAsString());
         }
 
         @Override
diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/metrics/avg/InternalAvg.java b/core/src/main/java/org/elasticsearch/search/aggregations/metrics/avg/InternalAvg.java
index 2c44a08b8a4..d6fe2e6a93e 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/metrics/avg/InternalAvg.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/metrics/avg/InternalAvg.java
@@ -96,9 +96,9 @@ public class InternalAvg extends InternalNumericMetricsAggregation.SingleValue i
 
     @Override
     public XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
-        builder.field(CommonFields.VALUE, count != 0 ? getValue() : null);
+        builder.field(CommonFields.VALUE.getPreferredName(), count != 0 ? getValue() : null);
         if (count != 0 && format != DocValueFormat.RAW) {
-            builder.field(CommonFields.VALUE_AS_STRING, format.format(getValue()));
+            builder.field(CommonFields.VALUE_AS_STRING.getPreferredName(), format.format(getValue()));
         }
         return builder;
     }
@@ -115,5 +115,4 @@ public class InternalAvg extends InternalNumericMetricsAggregation.SingleValue i
                 Objects.equals(count, other.count) &&
                 Objects.equals(format.getWriteableName(), other.format.getWriteableName());
     }
-
 }
diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/metrics/cardinality/InternalCardinality.java b/core/src/main/java/org/elasticsearch/search/aggregations/metrics/cardinality/InternalCardinality.java
index 02953abc2da..68e8935616f 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/metrics/cardinality/InternalCardinality.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/metrics/cardinality/InternalCardinality.java
@@ -109,7 +109,7 @@ public final class InternalCardinality extends InternalNumericMetricsAggregation
     @Override
     public XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
         final long cardinality = getValue();
-        builder.field(CommonFields.VALUE, cardinality);
+        builder.field(CommonFields.VALUE.getPreferredName(), cardinality);
         return builder;
     }
 
diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/metrics/max/InternalMax.java b/core/src/main/java/org/elasticsearch/search/aggregations/metrics/max/InternalMax.java
index c1634fdce4b..112d3793627 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/metrics/max/InternalMax.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/metrics/max/InternalMax.java
@@ -83,9 +83,9 @@ public class InternalMax extends InternalNumericMetricsAggregation.SingleValue i
     @Override
     public XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
         boolean hasValue = !Double.isInfinite(max);
-        builder.field(CommonFields.VALUE, hasValue ? max : null);
+        builder.field(CommonFields.VALUE.getPreferredName(), hasValue ? max : null);
         if (hasValue && format != DocValueFormat.RAW) {
-            builder.field(CommonFields.VALUE_AS_STRING, format.format(max));
+            builder.field(CommonFields.VALUE_AS_STRING.getPreferredName(), format.format(max));
         }
         return builder;
     }
diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/metrics/min/InternalMin.java b/core/src/main/java/org/elasticsearch/search/aggregations/metrics/min/InternalMin.java
index 46481d1837f..dcf180dde89 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/metrics/min/InternalMin.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/metrics/min/InternalMin.java
@@ -83,9 +83,9 @@ public class InternalMin extends InternalNumericMetricsAggregation.SingleValue i
     @Override
     public XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
         boolean hasValue = !Double.isInfinite(min);
-        builder.field(CommonFields.VALUE, hasValue ? min : null);
+        builder.field(CommonFields.VALUE.getPreferredName(), hasValue ? min : null);
         if (hasValue && format != DocValueFormat.RAW) {
-            builder.field(CommonFields.VALUE_AS_STRING, format.format(min));
+            builder.field(CommonFields.VALUE_AS_STRING.getPreferredName(), format.format(min));
         }
         return builder;
     }
diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/metrics/percentiles/hdr/AbstractInternalHDRPercentiles.java b/core/src/main/java/org/elasticsearch/search/aggregations/metrics/percentiles/hdr/AbstractInternalHDRPercentiles.java
index 892c6f2987e..29b8c38062c 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/metrics/percentiles/hdr/AbstractInternalHDRPercentiles.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/metrics/percentiles/hdr/AbstractInternalHDRPercentiles.java
@@ -115,7 +115,7 @@ abstract class AbstractInternalHDRPercentiles extends InternalNumericMetricsAggr
     @Override
     public XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
         if (keyed) {
-            builder.startObject(CommonFields.VALUES);
+            builder.startObject(CommonFields.VALUES.getPreferredName());
             for(int i = 0; i < keys.length; ++i) {
                 String key = String.valueOf(keys[i]);
                 double value = value(keys[i]);
@@ -126,14 +126,14 @@ abstract class AbstractInternalHDRPercentiles extends InternalNumericMetricsAggr
             }
             builder.endObject();
         } else {
-            builder.startArray(CommonFields.VALUES);
+            builder.startArray(CommonFields.VALUES.getPreferredName());
             for (int i = 0; i < keys.length; i++) {
                 double value = value(keys[i]);
                 builder.startObject();
-                builder.field(CommonFields.KEY, keys[i]);
-                builder.field(CommonFields.VALUE, value);
+                builder.field(CommonFields.KEY.getPreferredName(), keys[i]);
+                builder.field(CommonFields.VALUE.getPreferredName(), value);
                 if (format != DocValueFormat.RAW) {
-                    builder.field(CommonFields.VALUE_AS_STRING, format.format(value));
+                    builder.field(CommonFields.VALUE_AS_STRING.getPreferredName(), format.format(value));
                 }
                 builder.endObject();
             }
diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/metrics/percentiles/tdigest/AbstractInternalTDigestPercentiles.java b/core/src/main/java/org/elasticsearch/search/aggregations/metrics/percentiles/tdigest/AbstractInternalTDigestPercentiles.java
index 2d555edfb14..687b5533ecb 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/metrics/percentiles/tdigest/AbstractInternalTDigestPercentiles.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/metrics/percentiles/tdigest/AbstractInternalTDigestPercentiles.java
@@ -98,7 +98,7 @@ abstract class AbstractInternalTDigestPercentiles extends InternalNumericMetrics
     @Override
     public XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
         if (keyed) {
-            builder.startObject(CommonFields.VALUES);
+            builder.startObject(CommonFields.VALUES.getPreferredName());
             for(int i = 0; i < keys.length; ++i) {
                 String key = String.valueOf(keys[i]);
                 double value = value(keys[i]);
@@ -109,14 +109,14 @@ abstract class AbstractInternalTDigestPercentiles extends InternalNumericMetrics
             }
             builder.endObject();
         } else {
-            builder.startArray(CommonFields.VALUES);
+            builder.startArray(CommonFields.VALUES.getPreferredName());
             for (int i = 0; i < keys.length; i++) {
                 double value = value(keys[i]);
                 builder.startObject();
-                builder.field(CommonFields.KEY, keys[i]);
-                builder.field(CommonFields.VALUE, value);
+                builder.field(CommonFields.KEY.getPreferredName(), keys[i]);
+                builder.field(CommonFields.VALUE.getPreferredName(), value);
                 if (format != DocValueFormat.RAW) {
-                    builder.field(CommonFields.VALUE_AS_STRING, format.format(value));
+                    builder.field(CommonFields.VALUE_AS_STRING.getPreferredName(), format.format(value));
                 }
                 builder.endObject();
             }
diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/metrics/sum/InternalSum.java b/core/src/main/java/org/elasticsearch/search/aggregations/metrics/sum/InternalSum.java
index a93b41543ce..576f1ea52cf 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/metrics/sum/InternalSum.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/metrics/sum/InternalSum.java
@@ -82,9 +82,9 @@ public class InternalSum extends InternalNumericMetricsAggregation.SingleValue i
 
     @Override
     public XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
-        builder.field(CommonFields.VALUE, sum);
+        builder.field(CommonFields.VALUE.getPreferredName(), sum);
         if (format != DocValueFormat.RAW) {
-            builder.field(CommonFields.VALUE_AS_STRING, format.format(sum));
+            builder.field(CommonFields.VALUE_AS_STRING.getPreferredName(), format.format(sum));
         }
         return builder;
     }
diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/metrics/valuecount/InternalValueCount.java b/core/src/main/java/org/elasticsearch/search/aggregations/metrics/valuecount/InternalValueCount.java
index 25dd4e2e123..0ac42ff9f45 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/metrics/valuecount/InternalValueCount.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/metrics/valuecount/InternalValueCount.java
@@ -81,7 +81,7 @@ public class InternalValueCount extends InternalNumericMetricsAggregation.Single
 
     @Override
     public XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
-        builder.field(CommonFields.VALUE, value);
+        builder.field(CommonFields.VALUE.getPreferredName(), value);
         return builder;
     }
 
diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/pipeline/InternalSimpleValue.java b/core/src/main/java/org/elasticsearch/search/aggregations/pipeline/InternalSimpleValue.java
index b9d79b8e329..0f8eec4e66a 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/pipeline/InternalSimpleValue.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/pipeline/InternalSimpleValue.java
@@ -79,9 +79,9 @@ public class InternalSimpleValue extends InternalNumericMetricsAggregation.Singl
     @Override
     public XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
         boolean hasValue = !(Double.isInfinite(value) || Double.isNaN(value));
-        builder.field(CommonFields.VALUE, hasValue ? value : null);
+        builder.field(CommonFields.VALUE.getPreferredName(), hasValue ? value : null);
         if (hasValue && format != DocValueFormat.RAW) {
-            builder.field(CommonFields.VALUE_AS_STRING, format.format(value));
+            builder.field(CommonFields.VALUE_AS_STRING.getPreferredName(), format.format(value));
         }
         return builder;
     }
diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/pipeline/bucketmetrics/InternalBucketMetricValue.java b/core/src/main/java/org/elasticsearch/search/aggregations/pipeline/bucketmetrics/InternalBucketMetricValue.java
index 6477728b323..76284d27555 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/pipeline/bucketmetrics/InternalBucketMetricValue.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/pipeline/bucketmetrics/InternalBucketMetricValue.java
@@ -97,9 +97,9 @@ public class InternalBucketMetricValue extends InternalNumericMetricsAggregation
     @Override
     public XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
         boolean hasValue = !Double.isInfinite(value);
-        builder.field(CommonFields.VALUE, hasValue ? value : null);
+        builder.field(CommonFields.VALUE.getPreferredName(), hasValue ? value : null);
         if (hasValue && format != DocValueFormat.RAW) {
-            builder.field(CommonFields.VALUE_AS_STRING, format.format(value));
+            builder.field(CommonFields.VALUE_AS_STRING.getPreferredName(), format.format(value));
         }
         builder.startArray("keys");
         for (String key : keys) {