diff --git a/dlls/ntdll/file.c b/dlls/ntdll/file.c
index 3dee4ee..7a24b7f 100644
--- a/dlls/ntdll/file.c
+++ b/dlls/ntdll/file.c
@@ -2408,6 +2408,7 @@ NTSTATUS WINAPI NtLockFile( HANDLE hFile, HANDLE lock_granted_event,
     NTSTATUS    ret;
     HANDLE      handle;
     BOOLEAN     async;
+    static BOOLEAN     warn = TRUE;
 
     if (apc || io_status || key)
     {
@@ -2415,8 +2416,11 @@ NTSTATUS WINAPI NtLockFile( HANDLE hFile, HANDLE lock_granted_event,
         return STATUS_NOT_IMPLEMENTED;
     }
 
-    if (apc_user) FIXME("I/O completion on lock not implemented yet\n");
-
+    if (apc_user) 
+       if (warn) {
+           FIXME("I/O completion on lock not implemented yet\n");
+           warn = FALSE;
+       }
     for (;;)
     {
         SERVER_START_REQ( lock_file )