diff --git a/docs/content/querying/groupbyquery.md b/docs/content/querying/groupbyquery.md
index 61ff7031b02..2b90cda542e 100644
--- a/docs/content/querying/groupbyquery.md
+++ b/docs/content/querying/groupbyquery.md
@@ -205,4 +205,5 @@ When using the "v2" strategy, the following query context parameters apply:
 |`groupByStrategy`|Overrides the value of `druid.query.groupBy.defaultStrategy` for this query.|
 |`bufferGrouperInitialBuckets`|Overrides the value of `druid.query.groupBy.bufferGrouperInitialBuckets` for this query.|
 |`bufferGrouperMaxLoadFactor`|Overrides the value of `druid.query.groupBy.bufferGrouperMaxLoadFactor` for this query.|
+|`maxMergingDictionarySize`|Can be used to lower the value of `druid.query.groupBy.maxMergingDictionarySize` for this query.|
 |`maxOnDiskStorage`|Can be used to lower the value of `druid.query.groupBy.maxOnDiskStorage` for this query.|
diff --git a/processing/src/main/java/io/druid/query/groupby/GroupByQueryConfig.java b/processing/src/main/java/io/druid/query/groupby/GroupByQueryConfig.java
index 4b71baa90f5..6f3c3379440 100644
--- a/processing/src/main/java/io/druid/query/groupby/GroupByQueryConfig.java
+++ b/processing/src/main/java/io/druid/query/groupby/GroupByQueryConfig.java
@@ -34,6 +34,7 @@ public class GroupByQueryConfig
   private static final String CTX_KEY_BUFFER_GROUPER_MAX_LOAD_FACTOR = "bufferGrouperMaxLoadFactor";
   private static final String CTX_KEY_BUFFER_GROUPER_MAX_SIZE = "bufferGrouperMaxSize";
   private static final String CTX_KEY_MAX_ON_DISK_STORAGE = "maxOnDiskStorage";
+  private static final String CTX_KEY_MAX_MERGING_DICTIONARY_SIZE = "maxMergingDictionarySize";
 
   @JsonProperty
   private String defaultStrategy = GroupByStrategySelector.STRATEGY_V1;
@@ -151,9 +152,13 @@ public class GroupByQueryConfig
         getBufferGrouperInitialBuckets()
     );
     newConfig.maxOnDiskStorage = Math.min(
-        ((Number)query.getContextValue(CTX_KEY_MAX_ON_DISK_STORAGE, getMaxOnDiskStorage())).longValue(),
+        ((Number) query.getContextValue(CTX_KEY_MAX_ON_DISK_STORAGE, getMaxOnDiskStorage())).longValue(),
         getMaxOnDiskStorage()
     );
+    newConfig.maxMergingDictionarySize = Math.min(
+        ((Number) query.getContextValue(CTX_KEY_MAX_MERGING_DICTIONARY_SIZE, getMaxMergingDictionarySize())).longValue(),
+        getMaxMergingDictionarySize()
+    );
     return newConfig;
   }
 }
diff --git a/processing/src/test/java/io/druid/query/groupby/GroupByQueryConfigTest.java b/processing/src/test/java/io/druid/query/groupby/GroupByQueryConfigTest.java
new file mode 100644
index 00000000000..be080f2227c
--- /dev/null
+++ b/processing/src/test/java/io/druid/query/groupby/GroupByQueryConfigTest.java
@@ -0,0 +1,112 @@
+/*
+ * Licensed to Metamarkets Group Inc. (Metamarkets) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. Metamarkets licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package io.druid.query.groupby;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.google.common.collect.ImmutableMap;
+import io.druid.granularity.QueryGranularities;
+import io.druid.jackson.DefaultObjectMapper;
+import org.joda.time.Interval;
+import org.junit.Assert;
+import org.junit.Test;
+
+public class GroupByQueryConfigTest
+{
+  private final ObjectMapper MAPPER = new DefaultObjectMapper();
+
+  private final ImmutableMap<String, String> CONFIG_MAP = ImmutableMap
+      .<String, String>builder()
+      .put("singleThreaded", "true")
+      .put("defaultStrategy", "v2")
+      .put("bufferGrouperInitialBuckets", "1")
+      .put("maxIntermediateRows", "2")
+      .put("maxResults", "3")
+      .put("maxOnDiskStorage", "4")
+      .put("maxMergingDictionarySize", "5")
+      .put("bufferGrouperMaxLoadFactor", "6")
+      .build();
+
+  @Test
+  public void testSerde()
+  {
+    final GroupByQueryConfig config = MAPPER.convertValue(CONFIG_MAP, GroupByQueryConfig.class);
+
+    Assert.assertEquals(true, config.isSingleThreaded());
+    Assert.assertEquals("v2", config.getDefaultStrategy());
+    Assert.assertEquals(1, config.getBufferGrouperInitialBuckets());
+    Assert.assertEquals(2, config.getMaxIntermediateRows());
+    Assert.assertEquals(3, config.getMaxResults());
+    Assert.assertEquals(4, config.getMaxOnDiskStorage());
+    Assert.assertEquals(5, config.getMaxMergingDictionarySize());
+    Assert.assertEquals(6.0, config.getBufferGrouperMaxLoadFactor(), 0.0);
+  }
+
+  @Test
+  public void testNoOverrides()
+  {
+    final GroupByQueryConfig config = MAPPER.convertValue(CONFIG_MAP, GroupByQueryConfig.class);
+    final GroupByQueryConfig config2 = config.withOverrides(
+        GroupByQuery.builder()
+                    .setDataSource("test")
+                    .setInterval(new Interval("2000/P1D"))
+                    .setGranularity(QueryGranularities.ALL)
+                    .build()
+    );
+
+    Assert.assertEquals(true, config2.isSingleThreaded());
+    Assert.assertEquals("v2", config2.getDefaultStrategy());
+    Assert.assertEquals(1, config2.getBufferGrouperInitialBuckets());
+    Assert.assertEquals(2, config2.getMaxIntermediateRows());
+    Assert.assertEquals(3, config2.getMaxResults());
+    Assert.assertEquals(4, config2.getMaxOnDiskStorage());
+    Assert.assertEquals(5, config2.getMaxMergingDictionarySize());
+    Assert.assertEquals(6.0, config2.getBufferGrouperMaxLoadFactor(), 0.0);
+  }
+
+  @Test
+  public void testOverrides()
+  {
+    final GroupByQueryConfig config = MAPPER.convertValue(CONFIG_MAP, GroupByQueryConfig.class);
+    final GroupByQueryConfig config2 = config.withOverrides(
+        GroupByQuery.builder()
+                    .setDataSource("test")
+                    .setInterval(new Interval("2000/P1D"))
+                    .setGranularity(QueryGranularities.ALL)
+                    .setContext(
+                        ImmutableMap.<String, Object>of(
+                            "groupByStrategy", "v1",
+                            "maxOnDiskStorage", 0,
+                            "maxResults", 2,
+                            "maxMergingDictionarySize", 3
+                        )
+                    )
+                    .build()
+    );
+
+    Assert.assertEquals(true, config2.isSingleThreaded());
+    Assert.assertEquals("v1", config2.getDefaultStrategy());
+    Assert.assertEquals(1, config2.getBufferGrouperInitialBuckets());
+    Assert.assertEquals(2, config2.getMaxIntermediateRows());
+    Assert.assertEquals(2, config2.getMaxResults());
+    Assert.assertEquals(0, config2.getMaxOnDiskStorage());
+    Assert.assertEquals(3, config2.getMaxMergingDictionarySize());
+    Assert.assertEquals(6.0, config2.getBufferGrouperMaxLoadFactor(), 0.0);
+  }
+}