diff --git a/tests/test-check-rust-format.t b/tests/test-check-rust-format.t
--- a/tests/test-check-rust-format.t
+++ b/tests/test-check-rust-format.t
@@ -5,5 +5,5 @@
   $ cd "$TESTDIR"/..
   $ RUSTFMT=$(rustup which --toolchain nightly rustfmt)
   $ for f in `testrepohg files 'glob:**/*.rs'` ; do
-  >   $RUSTFMT --check --unstable-features --color=never $f
+  >   $RUSTFMT --check --edition=2018 --unstable-features --color=never $f
   > done