diff --git a/reactos/include/ndk/rtlfuncs.h b/reactos/include/ndk/rtlfuncs.h
index c6e15e117df..c18303d1cd4 100644
--- a/reactos/include/ndk/rtlfuncs.h
+++ b/reactos/include/ndk/rtlfuncs.h
@@ -4112,6 +4112,7 @@ RtlUnlockBootStatusData(
 #endif
 
 #ifdef NTOS_MODE_USER
+_Must_inspect_result_
 NTSYSAPI
 NTSTATUS
 NTAPI
@@ -4119,6 +4120,15 @@ RtlGUIDFromString(
     _In_ PUNICODE_STRING GuidString,
     _Out_ GUID *Guid);
 
+_Must_inspect_result_
+NTSYSAPI
+NTSTATUS
+NTAPI
+RtlStringFromGUID(
+  _In_ REFGUID Guid,
+  _Out_ _At_(GuidString->Buffer, __drv_allocatesMem(Mem))
+    PUNICODE_STRING GuidString);
+
 NTSYSAPI
 NTSTATUS
 NTAPI