diff --git a/src/modules/_Stdio/file.c b/src/modules/_Stdio/file.c
index ea7a49958806101a4e39949eee81e73cae78872f..f8f219817e5ac11ad9cff392e822ebd53a88ace4 100644
--- a/src/modules/_Stdio/file.c
+++ b/src/modules/_Stdio/file.c
@@ -5709,7 +5709,7 @@ static void exit_file_lock_key(struct object *DEBUGUSED(o))
     int fd=THIS_KEY->f->box.fd;
     int err;
 #ifdef PIKE_DEBUG
-    if(THIS_KEY->f->key != o)
+    if(THIS_KEY->f->key != 0)
       Pike_fatal("File lock key is wrong!\n");
 #endif