diff --git a/minimal_heap.h b/minimal_heap.h
index 8172c10..70ad352 100644
--- a/minimal_heap.h
+++ b/minimal_heap.h
@@ -25,7 +25,7 @@
 #endif
 
 #ifndef MIHP_HEAP_LOCK_TYPE
-	#define MIHP_HEAP_LOCK_TYPE bool // Does NOT have to be reentred safe
+	#define MIHP_HEAP_LOCK_TYPE volatile bool // Does NOT have to be reentred safe
 	#define MIHP_LOCK_HEAP(LockVarPtr) { while (*(LockVarPtr)) {}; *(LockVarPtr) = true; }
 	#define MIHP_UNLOCK_HEAP(LockVarPtr) { *(LockVarPtr) = false; }
 #endif