diff --git a/dll/win32/ntdll_vista/condvar.c b/dll/win32/ntdll_vista/condvar.c
index f14906d97d6..edbe074cd99 100644
--- a/dll/win32/ntdll_vista/condvar.c
+++ b/dll/win32/ntdll_vista/condvar.c
@@ -429,7 +429,7 @@ InternalSleep(IN OUT PRTL_CONDITION_VARIABLE ConditionVariable,
         }
     }
 
-#if _DEBUG
+#ifdef _DEBUG
     /* Clear OwnEntry to aid in detecting bugs. */
     RtlZeroMemory(&OwnEntry, sizeof(OwnEntry));
 #endif