diff --git a/processing/src/main/java/io/druid/segment/incremental/IncrementalIndex.java b/processing/src/main/java/io/druid/segment/incremental/IncrementalIndex.java
index 5427d1173a3..c19ad780337 100644
--- a/processing/src/main/java/io/druid/segment/incremental/IncrementalIndex.java
+++ b/processing/src/main/java/io/druid/segment/incremental/IncrementalIndex.java
@@ -442,6 +442,17 @@ public abstract class IncrementalIndex<AggregatorType> implements Iterable<Row>,
             overflow = Lists.newArrayList();
           }
           overflow.add(getDimVals(dimValues.add(dimension), dimensionValues));
+        } else if (index > dims.length || dims[index] != null)  {
+          /*
+           * index > dims.length requires that we saw this dimension and added it to the dimensionOrder map,
+           * otherwise index is null. Since dims is initialized based on the size of dimensionOrder on each call to add,
+           * it must have been added to dimensionOrder during this InputRow.
+           *
+           * if we found an index for this dimension it means we've seen it already. If !(index > dims.length) then
+           * we saw it on a previous input row (this its safe to index into dims). If we found a value in
+           * the dims array for this index, it means we have seen this dimension already on this input row.
+           */
+          throw new ISE("Dimension[%s] occurred more than once in InputRow", dimension);
         } else {
           dims[index] = getDimVals(dimValues.get(dimension), dimensionValues);
         }
diff --git a/processing/src/test/java/io/druid/segment/incremental/IncrementalIndexTest.java b/processing/src/test/java/io/druid/segment/incremental/IncrementalIndexTest.java
new file mode 100644
index 00000000000..5c182d41f58
--- /dev/null
+++ b/processing/src/test/java/io/druid/segment/incremental/IncrementalIndexTest.java
@@ -0,0 +1,147 @@
+/*
+ * Druid - a distributed column store.
+ * Copyright 2012 - 2015 Metamarkets Group Inc.
+ *
+ * Licensed 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.segment.incremental;
+
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.Lists;
+import com.metamx.common.ISE;
+import io.druid.data.input.MapBasedInputRow;
+import io.druid.granularity.QueryGranularity;
+import io.druid.query.TestQueryRunners;
+import io.druid.query.aggregation.AggregatorFactory;
+import io.druid.query.aggregation.CountAggregatorFactory;
+import org.joda.time.DateTime;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.Collection;
+
+/**
+ */
+@RunWith(Parameterized.class)
+public class IncrementalIndexTest
+{
+
+  interface IndexCreator
+  {
+    IncrementalIndex createIndex();
+  }
+
+  private final IndexCreator indexCreator;
+
+  public IncrementalIndexTest(IndexCreator IndexCreator)
+  {
+    this.indexCreator = IndexCreator;
+  }
+
+  @Parameterized.Parameters
+  public static Collection<?> constructorFeeder() throws IOException
+  {
+    return Arrays.asList(
+        new Object[][]{
+            {
+                new IndexCreator()
+                {
+                  @Override
+                  public IncrementalIndex createIndex()
+                  {
+                    return new OnheapIncrementalIndex(
+                        0, QueryGranularity.MINUTE, new AggregatorFactory[]{new CountAggregatorFactory("cnt")}, 1000
+                    );
+                  }
+                }
+
+            },
+            {
+                new IndexCreator()
+                {
+                  @Override
+                  public IncrementalIndex createIndex()
+                  {
+                    return new OffheapIncrementalIndex(
+                        0,
+                        QueryGranularity.MINUTE,
+                        new AggregatorFactory[]{new CountAggregatorFactory("cnt")},
+                        TestQueryRunners.pool,
+                        true,
+                        100 * 1024 * 1024
+                    );
+                  }
+                }
+            }
+
+        }
+    );
+  }
+
+  @Test(expected = ISE.class)
+  public void testDuplicateDimensions() throws IndexSizeExceededException
+  {
+    IncrementalIndex index = indexCreator.createIndex();
+    index.add(
+        new MapBasedInputRow(
+            new DateTime().minus(1).getMillis(),
+            Lists.newArrayList("billy", "joe"),
+            ImmutableMap.<String, Object>of("billy", "A", "joe", "B")
+        )
+    );
+    index.add(
+        new MapBasedInputRow(
+            new DateTime().minus(1).getMillis(),
+            Lists.newArrayList("billy", "joe", "joe"),
+            ImmutableMap.<String, Object>of("billy", "A", "joe", "B")
+        )
+    );
+  }
+
+  @Test(expected = ISE.class)
+  public void testDuplicateDimensionsFirstOccurance() throws IndexSizeExceededException
+  {
+    IncrementalIndex index = indexCreator.createIndex();
+    index.add(
+        new MapBasedInputRow(
+            new DateTime().minus(1).getMillis(),
+            Lists.newArrayList("billy", "joe", "joe"),
+            ImmutableMap.<String, Object>of("billy", "A", "joe", "B")
+        )
+    );
+  }
+
+  @Test
+  public void controlTest() throws IndexSizeExceededException
+  {
+    IncrementalIndex index = indexCreator.createIndex();
+    index.add(
+        new MapBasedInputRow(
+            new DateTime().minus(1).getMillis(),
+            Lists.newArrayList("billy", "joe"),
+            ImmutableMap.<String, Object>of("billy", "A", "joe", "B")
+        )
+    );
+    index.add(
+        new MapBasedInputRow(
+            new DateTime().minus(1).getMillis(),
+            Lists.newArrayList("billy", "joe"),
+            ImmutableMap.<String, Object>of("billy", "A", "joe", "B")
+        )
+    );
+  }
+}