diff --git a/reactos/include/win32k/gdiobj.h b/reactos/include/win32k/gdiobj.h
index 1dd9cd6bec1..3e33a23db84 100644
--- a/reactos/include/win32k/gdiobj.h
+++ b/reactos/include/win32k/gdiobj.h
@@ -103,6 +103,7 @@ PGDIOBJ INTERNAL_CALL GDIOBJ_ShareLockObjDbg (const char* file, int line, HGDIOB
 
 HGDIOBJ INTERNAL_CALL GDIOBJ_AllocObj(ULONG ObjectType);
 BOOL    INTERNAL_CALL GDIOBJ_FreeObj (HGDIOBJ hObj, DWORD ObjectType);
+PGDIOBJ INTERNAL_CALL GDIOBJ_LockObj (HGDIOBJ hObj, DWORD ObjectType);
 PGDIOBJ INTERNAL_CALL GDIOBJ_ShareLockObj (HGDIOBJ hObj, DWORD ObjectType);
 
 #endif /* GDI_DEBUG */