diff --git a/reactos/ntoskrnl/ke/gmutex.c b/reactos/ntoskrnl/ke/gmutex.c
index fc38a3b4e87..b94f7406f1a 100644
--- a/reactos/ntoskrnl/ke/gmutex.c
+++ b/reactos/ntoskrnl/ke/gmutex.c
@@ -123,7 +123,7 @@ KiReleaseGuardedMutex(IN OUT PKGUARDED_MUTEX GuardedMutex)
         
         /* The mutex will be woken, minus one waiter */
         NewValue = (OldValue | GM_LOCK_WAITER_WOKEN);
-        NewValue &= ~GM_LOCK_WAITER_INC;
+        NewValue -= GM_LOCK_WAITER_INC;
 
         /* Remove the Woken bit */
         if (InterlockedCompareExchange(&GuardedMutex->Count,