1 files changed, 6 insertions, 1 deletions
diff --git a/src/mongo/db/pipeline/document_source_sample.cpp b/src/mongo/db/pipeline/document_source_sample.cpp
index 5117e5c516a..c174d95d935 100644
--- a/src/mongo/db/pipeline/document_source_sample.cpp
+++ b/src/mongo/db/pipeline/document_source_sample.cpp
@@ -123,6 +123,11 @@ intrusive_ptr<DocumentSource> DocumentSourceSample::getShardSource() {
 
 intrusive_ptr<DocumentSource> DocumentSourceSample::getMergeSource() {
     // Just need to merge the pre-sorted documents by their random values.
-    return DocumentSourceSort::create(pExpCtx, randSortSpec, _size);
+    BSONObjBuilder randMergeSortSpec;
+
+    randMergeSortSpec.appendElements(randSortSpec);
+    randMergeSortSpec.append("$mergePresorted", true);
+
+    return DocumentSourceSort::create(pExpCtx, randMergeSortSpec.obj(), _size);
 }
 }  // mongo