diff --git a/contrib/pg_upgrade/server.c b/contrib/pg_upgrade/server.c
index d6efe9af6b43f39fbca0210292cd3bb8d11f15a5..224fc9642e9971c1ad99c2f6903b236826fdbc62 100644
--- a/contrib/pg_upgrade/server.c
+++ b/contrib/pg_upgrade/server.c
@@ -267,6 +267,7 @@ check_for_libpq_envvars(void)
 		{
 			const char *value;
 
+			/* This allows us to see error messages in the local encoding */
 			if (strcmp(option->envvar, "PGCLIENTENCODING") == 0)
 				continue;