diff --git a/src/mongo/s/chunk.cpp b/src/mongo/s/chunk.cpp
index a4bcd73cb367b..db22f5e40480e 100644
--- a/src/mongo/s/chunk.cpp
+++ b/src/mongo/s/chunk.cpp
@@ -616,7 +616,7 @@ namespace mongo {
         _splitHeuristics.markMinorForReload( getns(), majorVersion );
     }
 
-    void ChunkManager::getMarkedMinorVersions( set<ShardChunkVersion> minorVersions ) const {
+    void ChunkManager::getMarkedMinorVersions( set<ShardChunkVersion>& minorVersions ) const {
         _splitHeuristics.getMarkedMinorVersions( minorVersions );
     }
 
@@ -658,7 +658,7 @@ namespace mongo {
             grid.getDBConfig( ns )->getChunkManagerIfExists( ns, true, true );
     }
 
-    void ChunkManager::SplitHeuristics::getMarkedMinorVersions( set<ShardChunkVersion> minorVersions ) {
+    void ChunkManager::SplitHeuristics::getMarkedMinorVersions( set<ShardChunkVersion>& minorVersions ) {
         scoped_lock lk( _staleMinorSetMutex );
         for( set<ShardChunkVersion>::iterator it = _staleMinorSet.begin(); it != _staleMinorSet.end(); it++ ){
             minorVersions.insert( *it );
diff --git a/src/mongo/s/chunk.h b/src/mongo/s/chunk.h
index 53447c57ed2ff..23090261b1abb 100644
--- a/src/mongo/s/chunk.h
+++ b/src/mongo/s/chunk.h
@@ -361,7 +361,7 @@ namespace mongo {
     private:
         ChunkManagerPtr reload(bool force=true) const; // doesn't modify self!
         void markMinorForReload( ShardChunkVersion majorVersion ) const;
-        void getMarkedMinorVersions( set<ShardChunkVersion> minorVersions ) const;
+        void getMarkedMinorVersions( set<ShardChunkVersion>& minorVersions ) const;
 
         // helpers for constructor
         void _load(ChunkMap& chunks, set<Shard>& shards, ShardVersionMap& shardVersions, ChunkManagerPtr oldManager);
@@ -400,7 +400,7 @@ namespace mongo {
                 _staleMinorCount( 0 ) {}
 
             void markMinorForReload( const string& ns, ShardChunkVersion majorVersion );
-            void getMarkedMinorVersions( set<ShardChunkVersion> minorVersions );
+            void getMarkedMinorVersions( set<ShardChunkVersion>& minorVersions );
 
             TicketHolder _splitTickets;