diff --git a/src/backend/utils/activity/pgstat.c b/src/backend/utils/activity/pgstat.c
index f48b00b86bf..ed7baa6e046 100644
--- a/src/backend/utils/activity/pgstat.c
+++ b/src/backend/utils/activity/pgstat.c
@@ -1360,6 +1360,9 @@ pgstat_write_statsfile(void)
 
 	pgstat_assert_is_up();
 
+	/* should be called only by the checkpointer or single user mode */
+	Assert(!IsUnderPostmaster || MyBackendType == B_CHECKPOINTER);
+
 	/* we're shutting down, so it's ok to just override this */
 	pgstat_fetch_consistency = PGSTAT_FETCH_CONSISTENCY_NONE;