1 files changed, 8 insertions, 5 deletions

diff --git a/src/mongo/db/exec/sort.h b/src/mongo/db/exec/sort.h
index e67305504ba..96da33b36b7 100644
--- a/src/mongo/db/exec/sort.h
+++ b/src/mongo/db/exec/sort.h
@@ -47,9 +47,10 @@ namespace mongo {
     // Parameters that must be provided to a SortStage
     class SortStageParams {
     public:
-        SortStageParams() : collection( NULL), limit(0) { }
+        SortStageParams() : collection(NULL), limit(0) { }
 
-        Collection* collection;
+        // Used for resolving DiskLocs to BSON
+        const Collection* collection;
 
         // How we're sorting.
         BSONObj pattern;
@@ -73,7 +74,7 @@ namespace mongo {
          * ensure that the value we select to sort by is within bounds generated by
          * executing 'queryObj' using the virtual index with key pattern 'sortSpec'.
          */
-        SortStageKeyGenerator(Collection* collection,
+        SortStageKeyGenerator(const Collection* collection,
                               const BSONObj& sortSpec,
                               const BSONObj& queryObj);
 
@@ -104,7 +105,8 @@ namespace mongo {
         void getBoundsForSort(const BSONObj& queryObj,
                               const BSONObj& sortObj);
 
-        Collection* _collection;
+        // Not owned by us
+        const Collection* _collection;
 
         // The object that we use to call woCompare on our resulting key.  Is equal to _rawSortSpec
         // unless we have some $meta expressions.  Each $meta expression has a default sort order.
@@ -160,7 +162,8 @@ namespace mongo {
         // Query Stage
         //
 
-        Collection* _collection;
+        // Not owned by us.
+        const Collection* _collection;
 
         // Not owned by us.
         WorkingSet* _ws;