diff --git a/memory/heap.c b/memory/heap.c
index e4755abd292..6b00960c255 100644
--- a/memory/heap.c
+++ b/memory/heap.c
@@ -508,7 +508,12 @@ static BOOL HEAP_InitSubHeap( HEAP *heap, LPVOID address, DWORD flags,
         /* Initialize critical section */
 
         InitializeCriticalSection( &heap->critSection );
-        if (!SystemHeap) HEAP_SystemLock = &heap->critSection;
+        if (!SystemHeap)
+        {
+            HEAP_SystemLock = &heap->critSection;
+            /* System heap critical section has to be global */
+            MakeCriticalSectionGlobal( &heap->critSection );
+        }
     }
  
     /* Create the first free block */