diff --git a/velox/exec/MergeSource.h b/velox/exec/MergeSource.h
index e6bf01e4c611..db3da21ae50b 100644
--- a/velox/exec/MergeSource.h
+++ b/velox/exec/MergeSource.h
@@ -65,7 +65,7 @@ class MergeJoinSource {
 
  private:
   struct State {
-    bool atEnd;
+    bool atEnd = false;
     RowVectorPtr data;
   };