diff --git a/ci/fmt.sh b/ci/fmt.sh
index 04038462d..75c1f1924 100755
--- a/ci/fmt.sh
+++ b/ci/fmt.sh
@@ -3,5 +3,7 @@ set -eu
 . "$(dirname "$0")/sub/lib.sh"
 cd -- "$(dirname "$0")/.."
 
-sh_c tocsubst --skip 1 README.md
+if is_changed README.md; then
+  sh_c tocsubst --skip 1 README.md
+fi
 ./ci/sub/fmt/make.sh
diff --git a/ci/sub b/ci/sub
index a39a67857..e894a489a 160000
--- a/ci/sub
+++ b/ci/sub
@@ -1 +1 @@
-Subproject commit a39a678570a0454d6bf63f9012fb5ec107e24df5
+Subproject commit e894a489abaead7314a3f126cdb32f18b272a23f