couch_file:process_info can return `undefined`
diff --git a/src/couch_file.erl b/src/couch_file.erl
index d2b3960..8346b02 100644
--- a/src/couch_file.erl
+++ b/src/couch_file.erl
@@ -664,7 +664,7 @@
     end.
 
 -spec process_info(CouchFilePid :: pid()) ->
-    {Fd :: pid() | tuple(), FilePath :: string()}.
+    {Fd :: pid() | tuple(), FilePath :: string()} | undefined.
 
 process_info(Pid) ->
     {dictionary, Dict} = erlang:process_info(Pid, dictionary),