diff --git a/reactos/lib/rtl/heap.c b/reactos/lib/rtl/heap.c
index 6da4c4e88bb..b0bb0dfa8be 100644
--- a/reactos/lib/rtl/heap.c
+++ b/reactos/lib/rtl/heap.c
@@ -2645,7 +2645,7 @@ RtlReAllocateHeap(HANDLE HeapPtr,
     {
         RtlEnterHeapLock(Heap->LockVariable);
         HeapLocked = TRUE;
-        Flags &= ~HEAP_NO_SERIALIZE;
+        Flags ^= HEAP_NO_SERIALIZE;
     }
 
     /* Get the pointer to the in-use entry */