diff --git a/builtin/send-pack.c b/builtin/send-pack.c
index b7183be970..3df9eaad09 100644
--- a/builtin/send-pack.c
+++ b/builtin/send-pack.c
@@ -333,6 +333,7 @@ int cmd_send_pack(int argc, const char **argv, const char *prefix)
 	}
 
 	if (!ret && !transport_refs_pushed(remote_refs))
+		/* stable plumbing output; do not modify or localize */
 		fprintf(stderr, "Everything up-to-date\n");
 
 	return ret;
diff --git a/http-push.c b/http-push.c
index b4d0b2a6aa..12d1113741 100644
--- a/http-push.c
+++ b/http-push.c
@@ -1851,6 +1851,7 @@ int cmd_main(int argc, const char **argv)
 
 		if (oideq(&ref->old_oid, &ref->peer_ref->new_oid)) {
 			if (push_verbosely)
+				/* stable plumbing output; do not modify or localize */
 				fprintf(stderr, "'%s': up-to-date\n", ref->name);
 			if (helper_status)
 				printf("ok %s up to date\n", ref->name);
@@ -1871,6 +1872,7 @@ int cmd_main(int argc, const char **argv)
 				 * commits at the remote end and likely
 				 * we were not up to date to begin with.
 				 */
+				/* stable plumbing output; do not modify or localize */
 				error("remote '%s' is not an ancestor of\n"
 				      "local '%s'.\n"
 				      "Maybe you are not up-to-date and "
diff --git a/transport.c b/transport.c
index bd7899e9bf..df518ead70 100644
--- a/transport.c
+++ b/transport.c
@@ -1467,6 +1467,7 @@ int transport_push(struct repository *r,
 	if (porcelain && !push_ret)
 		puts("Done");
 	else if (!quiet && !ret && !transport_refs_pushed(remote_refs))
+		/* stable plumbing output; do not modify or localize */
 		fprintf(stderr, "Everything up-to-date\n");
 
 done: