diff --git a/src/main/java/org/elasticsearch/index/mapper/MergeContext.java b/src/main/java/org/elasticsearch/index/mapper/MergeContext.java
index 70ce553048e..72d9565432b 100644
--- a/src/main/java/org/elasticsearch/index/mapper/MergeContext.java
+++ b/src/main/java/org/elasticsearch/index/mapper/MergeContext.java
@@ -21,6 +21,8 @@ package org.elasticsearch.index.mapper;
 
 import com.google.common.collect.Lists;
 
+import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 
 /**
@@ -35,6 +37,8 @@ public class MergeContext {
     private final FieldMapperListener.Aggregator newFieldMappers = new FieldMapperListener.Aggregator();
     private final ObjectMapperListener.Aggregator newObjectMappers = new ObjectMapperListener.Aggregator();
 
+    private List<FieldMapper> fieldDataChanges = null;
+
     public MergeContext(DocumentMapper documentMapper, DocumentMapper.MergeFlags mergeFlags) {
         this.documentMapper = documentMapper;
         this.mergeFlags = mergeFlags;
@@ -67,4 +71,18 @@ public class MergeContext {
     public String[] buildConflicts() {
         return mergeConflicts.toArray(new String[mergeConflicts.size()]);
     }
+
+    public void addFieldDataChange(FieldMapper mapper) {
+        if (fieldDataChanges == null) {
+            fieldDataChanges = new ArrayList<FieldMapper>();
+        }
+        fieldDataChanges.add(mapper);
+    }
+
+    public List<FieldMapper> fieldMapperChanges() {
+        if (fieldDataChanges == null) {
+            return Collections.emptyList();
+        }
+        return fieldDataChanges;
+    }
 }
diff --git a/src/main/java/org/elasticsearch/index/mapper/core/AbstractFieldMapper.java b/src/main/java/org/elasticsearch/index/mapper/core/AbstractFieldMapper.java
index 5223f777b3e..afad2f9d1f6 100644
--- a/src/main/java/org/elasticsearch/index/mapper/core/AbstractFieldMapper.java
+++ b/src/main/java/org/elasticsearch/index/mapper/core/AbstractFieldMapper.java
@@ -19,6 +19,7 @@
 
 package org.elasticsearch.index.mapper.core;
 
+import com.google.common.base.Objects;
 import org.apache.lucene.analysis.Analyzer;
 import org.apache.lucene.document.Field;
 import org.apache.lucene.document.FieldType;
@@ -583,10 +584,13 @@ public abstract class AbstractFieldMapper<T> implements FieldMapper<T>, Mapper {
                 this.postingsFormat = fieldMergeWith.postingsFormat;
             }
             if (fieldMergeWith.customFieldDataSettings != null) {
-                this.customFieldDataSettings = fieldMergeWith.customFieldDataSettings;
-                this.fieldDataType = new FieldDataType(defaultFieldDataType().getType(),
-                        ImmutableSettings.builder().put(defaultFieldDataType().getSettings()).put(this.customFieldDataSettings)
-                );
+                if (!Objects.equal(fieldMergeWith.customFieldDataSettings, this.customFieldDataSettings)) {
+                    this.customFieldDataSettings = fieldMergeWith.customFieldDataSettings;
+                    this.fieldDataType = new FieldDataType(defaultFieldDataType().getType(),
+                            ImmutableSettings.builder().put(defaultFieldDataType().getSettings()).put(this.customFieldDataSettings)
+                    );
+                    mergeContext.addFieldDataChange(this);
+                }
             }
         }
     }