diff --git a/paw/stos/head/hal/intr.h b/paw/stos/head/hal/intr.h
index d000020..bc4bec3 100644
--- a/paw/stos/head/hal/intr.h
+++ b/paw/stos/head/hal/intr.h
@@ -18,13 +18,15 @@
  * @IRQL_PASSIVE:   Standard user/kernel operation
  * @IRQL_APC:       Asynchronous procedure call
  * @IRQL_DISPATCH:  Deferred procedure call dispatch
+ * @IRQL_CRITICAL:  Critical section
  * @IRQL_HIGH:      Block everything
  */
 #define IRQL_PASSIVE  0
 #define IRQL_APC      1
 #define IRQL_DISPATCH 2
 #define IRQL_DEVICE   3
-#define IRQL_HIGH     4
+#define IRQL_CRITICAL 4
+#define IRQL_HIGH     5
 
 /* IRQLs are of this type */
 typedef UCHAR IRQL;