diff --git a/common/src/main/java/com/metamx/druid/partition/PartitionHolder.java b/common/src/main/java/com/metamx/druid/partition/PartitionHolder.java
index 00dc3e18a43..79d1b5dd96e 100644
--- a/common/src/main/java/com/metamx/druid/partition/PartitionHolder.java
+++ b/common/src/main/java/com/metamx/druid/partition/PartitionHolder.java
@@ -61,6 +61,11 @@ public class PartitionHolder<T> implements Iterable<PartitionChunk<T>>
     holderSet.add(chunk);
   }
 
+  public int size()
+  {
+    return holderSet.size();
+  }
+
   public PartitionChunk<T> remove(PartitionChunk<T> chunk)
   {
     // Somewhat funky implementation in order to return the removed object as it exists in the set
diff --git a/server/src/main/java/com/metamx/druid/master/DruidMasterSegmentMerger.java b/server/src/main/java/com/metamx/druid/master/DruidMasterSegmentMerger.java
index 8be132b9400..e46c2a06f51 100644
--- a/server/src/main/java/com/metamx/druid/master/DruidMasterSegmentMerger.java
+++ b/server/src/main/java/com/metamx/druid/master/DruidMasterSegmentMerger.java
@@ -38,6 +38,7 @@ import com.metamx.druid.VersionedIntervalTimeline;
 import com.metamx.druid.client.DataSegment;
 import com.metamx.druid.client.indexing.IndexingServiceClient;
 import com.metamx.druid.partition.PartitionChunk;
+import com.metamx.druid.shard.NoneShardSpec;
 import org.joda.time.DateTime;
 import org.joda.time.Interval;
 
@@ -98,16 +99,8 @@ public class DruidMasterSegmentMerger implements DruidMasterHelper
       SegmentsToMerge segmentsToMerge = new SegmentsToMerge();
 
       for (int i = 0; i < timelineObjects.size(); i++) {
-
-        try {
-          segmentsToMerge.add(timelineObjects.get(i));
-        }
-        catch (Exception e) {
-          log.error("Unable to merge segments for %s", entry.getKey());
-          throw Throwables.propagate(e);
-        }
-
-        if (segmentsToMerge.getByteCount() > params.getMergeBytesLimit()
+        if (!segmentsToMerge.add(timelineObjects.get(i))
+            || segmentsToMerge.getByteCount() > params.getMergeBytesLimit()
             || segmentsToMerge.getSegmentCount() >= params.getMergeSegmentsLimit()) {
           i -= segmentsToMerge.backtrack(params.getMergeBytesLimit());
 
@@ -216,7 +209,7 @@ public class DruidMasterSegmentMerger implements DruidMasterHelper
       ).asList();
     }
 
-    public void add(TimelineObjectHolder<String, DataSegment> timelineObject)
+    public boolean add(TimelineObjectHolder<String, DataSegment> timelineObject)
     {
       final Interval timelineObjectInterval = timelineObject.getInterval();
 
@@ -235,6 +228,10 @@ public class DruidMasterSegmentMerger implements DruidMasterHelper
       Interval underlyingInterval = firstChunk.getObject().getInterval();
 
       for (final PartitionChunk<DataSegment> segment : timelineObject.getObject()) {
+        if (!(segment.getObject().getShardSpec() instanceof NoneShardSpec)) {
+          return false;
+        }
+
         segments.add(segment.getObject());
         if (segments.count(segment.getObject()) == 1) {
           byteCount += segment.getObject().getSize();
@@ -256,6 +253,8 @@ public class DruidMasterSegmentMerger implements DruidMasterHelper
 
         timelineObjects.add(Pair.of(timelineObject, new Interval(start, end)));
       }
+
+      return true;
     }
 
     public Interval getMergedTimelineInterval()
diff --git a/server/src/test/java/com/metamx/druid/master/DruidMasterSegmentMergerTest.java b/server/src/test/java/com/metamx/druid/master/DruidMasterSegmentMergerTest.java
index 44cac2ad19e..f8bbdcc63f8 100644
--- a/server/src/test/java/com/metamx/druid/master/DruidMasterSegmentMergerTest.java
+++ b/server/src/test/java/com/metamx/druid/master/DruidMasterSegmentMergerTest.java
@@ -397,7 +397,45 @@ public class DruidMasterSegmentMergerTest
     );
 
     Assert.assertEquals(
-        ImmutableList.of(ImmutableList.of(segments.get(0), segments.get(1), segments.get(2))),
+        ImmutableList.of(),
+        merge(segments)
+    );
+  }
+
+  @Test
+  public void testMergeMixedShardSpecs()
+  {
+    final List<DataSegment> segments = ImmutableList.of(
+        DataSegment.builder()
+                   .dataSource("foo")
+                   .interval(new Interval("2012-01-01/P1D"))
+                   .version("1")
+                   .build(),
+        DataSegment.builder()
+                   .dataSource("foo")
+                   .interval(new Interval("2012-01-02/P1D"))
+                   .version("1")
+                   .build(),
+        DataSegment.builder().dataSource("foo")
+                   .interval(new Interval("2012-01-03/P1D"))
+                   .version("1")
+                   .shardSpec(new LinearShardSpec(1500))
+                   .build(),
+        DataSegment.builder().dataSource("foo")
+                   .interval(new Interval("2012-01-04/P1D"))
+                   .version("1")
+                   .build(),
+        DataSegment.builder().dataSource("foo")
+                   .interval(new Interval("2012-01-05/P1D"))
+                   .version("1")
+                   .build()
+    );
+
+    Assert.assertEquals(
+        ImmutableList.of(
+            ImmutableList.of(segments.get(0), segments.get(1)),
+            ImmutableList.of(segments.get(3), segments.get(4))
+        ),
         merge(segments)
     );
   }