diff --git a/reactos/sdk/include/ndk/rtltypes.h b/reactos/sdk/include/ndk/rtltypes.h
index ad0702c7395..46f1787d35f 100644
--- a/reactos/sdk/include/ndk/rtltypes.h
+++ b/reactos/sdk/include/ndk/rtltypes.h
@@ -1438,7 +1438,7 @@ typedef enum _RTL_UMS_SCHEDULER_REASON
     UmsSchedulerThreadYield = 2,
 } RTL_UMS_SCHEDULER_REASON, *PRTL_UMS_SCHEDULER_REASON;
 
-enum _RTL_UMSCTX_FLAGS
+typedef enum _RTL_UMSCTX_FLAGS
 {
     UMSCTX_SCHEDULED_THREAD_BIT = 0,
 #if (NTDDI_VERSION < NTDDI_WIN8)