diff --git a/reactos/ntoskrnl/ke/i386/usercall_asm.S b/reactos/ntoskrnl/ke/i386/usercall_asm.S
index 03f5a2114ee..161f3c25fdf 100644
--- a/reactos/ntoskrnl/ke/i386/usercall_asm.S
+++ b/reactos/ntoskrnl/ke/i386/usercall_asm.S
@@ -87,7 +87,6 @@ _KiCallUserMode@8:
 
 AtPassive:
 
-#if 0
     /* Make sure that we are not attached and that APCs are not disabled */
     movzx eax, byte ptr [ebx+KTHREAD_APC_STATE_INDEX]
     mov edx, [ebx+KTHREAD_COMBINED_APC_DISABLE]
@@ -104,7 +103,6 @@ InvalidIndex:
     push 0
     push APC_INDEX_MISMATCH
     call _KeBugCheckEx@20
-#endif
 ApcsEnabled:
 #endif
 
diff --git a/reactos/subsys/win32k/ntuser/msgqueue.c b/reactos/subsys/win32k/ntuser/msgqueue.c
index 2b2c7f46ca2..2ea5cd8632a 100644
--- a/reactos/subsys/win32k/ntuser/msgqueue.c
+++ b/reactos/subsys/win32k/ntuser/msgqueue.c
@@ -46,7 +46,7 @@ static KSPIN_LOCK SystemMessageQueueLock;
 
 static ULONG volatile HardwareMessageQueueStamp = 0;
 static LIST_ENTRY HardwareMessageQueueHead;
-static KMUTEX HardwareMessageQueueLock;
+static KMUTANT HardwareMessageQueueLock;
 
 static KEVENT HardwareMessageEvent;
 
@@ -60,7 +60,7 @@ static PAGED_LOOKASIDE_LIST TimerLookasideList;
   KeReleaseSpinLock(&SystemMessageQueueLock, OldIrql)
 
 #define IntUnLockSystemHardwareMessageQueueLock(Wait) \
-  KeReleaseMutex(&HardwareMessageQueueLock, Wait)
+  KeReleaseMutant(&HardwareMessageQueueLock, IO_NO_INCREMENT, FALSE, Wait)
 
 /* FUNCTIONS *****************************************************************/
 
@@ -122,7 +122,7 @@ MsqInitializeImpl(VOID)
    InitializeListHead(&HardwareMessageQueueHead);
    KeInitializeEvent(&HardwareMessageEvent, NotificationEvent, 0);
    KeInitializeSpinLock(&SystemMessageQueueLock);
-   KeInitializeMutex(&HardwareMessageQueueLock, 0);
+   KeInitializeMutant(&HardwareMessageQueueLock, 0);
 
    ExInitializePagedLookasideList(&MessageLookasideList,
                                   NULL,