diff --git a/ci/test-stable.sh b/ci/test-stable.sh
index 9c31a3afda..faf6f73784 100755
--- a/ci/test-stable.sh
+++ b/ci/test-stable.sh
@@ -12,7 +12,7 @@ _() {
 }
 
 _ rustup component add rustfmt-preview
-_ cargo fmt -- --write-mode=diff
+_ cargo fmt -- --write-mode=check
 _ cargo build --verbose
 _ cargo test --verbose
 _ cargo test -- --ignored