--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -2042,6 +2042,11 @@ make_template0(FILE *cmdfd)
 		 * Finally vacuum to clean up dead rows in pg_database
 		 */
 		"VACUUM pg_database;\n\n",
+
+		/*
+		 * And rebuild pg_class.
+		 */
+		"VACUUM FULL pg_class;\n\n",
 		NULL
 	};