diff --git a/processing/src/main/java/io/druid/query/aggregation/JavaScriptAggregatorFactory.java b/processing/src/main/java/io/druid/query/aggregation/JavaScriptAggregatorFactory.java
index d54425d343b..0d33bf1ad30 100644
--- a/processing/src/main/java/io/druid/query/aggregation/JavaScriptAggregatorFactory.java
+++ b/processing/src/main/java/io/druid/query/aggregation/JavaScriptAggregatorFactory.java
@@ -278,7 +278,7 @@ public class JavaScriptAggregatorFactory implements AggregatorFactory
           final ObjectColumnSelector selector = selectorList[i];
           if (selector != null) {
             final Object arg = selector.get();
-            if (arg.getClass().isArray()) {
+            if (arg != null && arg.getClass().isArray()) {
               // Context.javaToJS on an array sort of works, although it returns false for Array.isArray(...) and
               // may have other issues too. Let's just copy the array and wrap that.
               final Object[] arrayAsObjectArray = new Object[Array.getLength(arg)];
diff --git a/processing/src/main/java/io/druid/segment/QueryableIndexStorageAdapter.java b/processing/src/main/java/io/druid/segment/QueryableIndexStorageAdapter.java
index b3178d83df7..fd772ea4770 100644
--- a/processing/src/main/java/io/druid/segment/QueryableIndexStorageAdapter.java
+++ b/processing/src/main/java/io/druid/segment/QueryableIndexStorageAdapter.java
@@ -467,23 +467,29 @@ public class QueryableIndexStorageAdapter implements StorageAdapter
                       if (cachedColumnVals instanceof DictionaryEncodedColumn) {
                         final DictionaryEncodedColumn columnVals = (DictionaryEncodedColumn) cachedColumnVals;
                         if (columnVals.hasMultipleValues()) {
-                          return new ObjectColumnSelector<String[]>()
+                          return new ObjectColumnSelector<Object>()
                           {
                             @Override
                             public Class classOfObject()
                             {
-                              return String[].class;
+                              return Object.class;
                             }
 
                             @Override
-                            public String[] get()
+                            public Object get()
                             {
                               final IndexedInts multiValueRow = columnVals.getMultiValueRow(cursorOffset.getOffset());
-                              final String[] strings = new String[multiValueRow.size()];
-                              for (int i = 0 ; i < multiValueRow.size() ; i++) {
-                                strings[i] = columnVals.lookupName(multiValueRow.get(i));
+                              if (multiValueRow.size() == 0) {
+                                return null;
+                              } else if (multiValueRow.size() == 1) {
+                                return columnVals.lookupName(multiValueRow.get(1));
+                              } else {
+                                final String[] strings = new String[multiValueRow.size()];
+                                for (int i = 0 ; i < multiValueRow.size() ; i++) {
+                                  strings[i] = columnVals.lookupName(multiValueRow.get(i));
+                                }
+                                return strings;
                               }
-                              return strings;
                             }
                           };
                         } else {
@@ -891,23 +897,29 @@ public class QueryableIndexStorageAdapter implements StorageAdapter
                       if (cachedColumnVals instanceof DictionaryEncodedColumn) {
                         final DictionaryEncodedColumn columnVals = (DictionaryEncodedColumn) cachedColumnVals;
                         if (columnVals.hasMultipleValues()) {
-                          return new ObjectColumnSelector<String[]>()
+                          return new ObjectColumnSelector<Object>()
                           {
                             @Override
                             public Class classOfObject()
                             {
-                              return String[].class;
+                              return Object.class;
                             }
 
                             @Override
-                            public String[] get()
+                            public Object get()
                             {
                               final IndexedInts multiValueRow = columnVals.getMultiValueRow(currRow);
-                              final String[] strings = new String[multiValueRow.size()];
-                              for (int i = 0 ; i < multiValueRow.size() ; i++) {
-                                strings[i] = columnVals.lookupName(multiValueRow.get(i));
+                              if (multiValueRow.size() == 0) {
+                                return null;
+                              } else if (multiValueRow.size() == 1) {
+                                return columnVals.lookupName(multiValueRow.get(1));
+                              } else {
+                                final String[] strings = new String[multiValueRow.size()];
+                                for (int i = 0 ; i < multiValueRow.size() ; i++) {
+                                  strings[i] = columnVals.lookupName(multiValueRow.get(i));
+                                }
+                                return strings;
                               }
-                              return strings;
                             }
                           };
                         } else {
diff --git a/processing/src/main/java/io/druid/segment/incremental/IncrementalIndexStorageAdapter.java b/processing/src/main/java/io/druid/segment/incremental/IncrementalIndexStorageAdapter.java
index d4c3dad7a7a..7ff26a789a8 100644
--- a/processing/src/main/java/io/druid/segment/incremental/IncrementalIndexStorageAdapter.java
+++ b/processing/src/main/java/io/druid/segment/incremental/IncrementalIndexStorageAdapter.java
@@ -408,11 +408,7 @@ public class IncrementalIndexStorageAdapter implements StorageAdapter
                             @Override
                             public Class classOfObject()
                             {
-                              if (currEntry.getKey().getDims()[dimensionIndex].length > 1) {
-                                return String[].class;
-                              } else {
-                                return String.class;
-                              }
+                              return Object.class;
                             }
 
                             @Override
diff --git a/processing/src/test/java/io/druid/query/aggregation/JavaScriptAggregatorTest.java b/processing/src/test/java/io/druid/query/aggregation/JavaScriptAggregatorTest.java
index 36250b18e41..d53ea6d1235 100644
--- a/processing/src/test/java/io/druid/query/aggregation/JavaScriptAggregatorTest.java
+++ b/processing/src/test/java/io/druid/query/aggregation/JavaScriptAggregatorTest.java
@@ -184,12 +184,12 @@ public class JavaScriptAggregatorTest
   @Test
   public void testAggregateStrings()
   {
-    final TestObjectColumnSelector ocs = new TestObjectColumnSelector("what", new String[]{"hey", "there"});
+    final TestObjectColumnSelector ocs = new TestObjectColumnSelector("what", null, new String[]{"hey", "there"});
     final JavaScriptAggregator agg = new JavaScriptAggregator(
         "billy",
         Collections.<ObjectColumnSelector>singletonList(ocs),
         JavaScriptAggregatorFactory.compileScript(
-            "function aggregate(current, a) { if (typeof a === 'string') { return current + 1; } else { return current + a.length; } }",
+            "function aggregate(current, a) { if (Array.isArray(a)) { return current + a.length; } else if (typeof a === 'string') { return current + 1; } else { return current; } }",
             scriptDoubleSum.get("fnReset"),
             scriptDoubleSum.get("fnCombine")
         )
@@ -211,6 +211,11 @@ public class JavaScriptAggregatorTest
     Assert.assertEquals(val, agg.get());
     aggregate(ocs, agg);
 
+    Assert.assertEquals(val, agg.get());
+    Assert.assertEquals(val, agg.get());
+    Assert.assertEquals(val, agg.get());
+    aggregate(ocs, agg);
+
     val += 2;
     Assert.assertEquals(val, agg.get());
     Assert.assertEquals(val, agg.get());