1 files changed, 2 insertions, 0 deletions
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index f249e1e8cb..d3b14c17fc 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -6755,6 +6755,8 @@ posix_fdopen(PyObject *self, PyObject *args)
     PyMem_FREE(mode);
     if (fp == NULL)
         return posix_error();
+    /* The dummy filename used here must be kept in sync with the value
+       tested against in gzip.GzipFile.__init__() - see issue #13781. */
     f = PyFile_FromFile(fp, "<fdopen>", orgmode, fclose);
     if (f != NULL)
         PyFile_SetBufSize(f, bufsize);