diff --git a/reactos/ntoskrnl/ex/fmutex.c b/reactos/ntoskrnl/ex/fmutex.c
index 2c574e004d4..947d3f723b1 100644
--- a/reactos/ntoskrnl/ex/fmutex.c
+++ b/reactos/ntoskrnl/ex/fmutex.c
@@ -106,7 +106,7 @@ VOID
 FASTCALL
 ExReleaseFastMutex (PFAST_MUTEX FastMutex)
 {
-    KIRQL oldIrql;
+    KIRQL OldIrql;
     ASSERT_IRQL(APC_LEVEL);
 
     /* Erase the owner */