diff --git a/library/compiler-builtins/libm/.github/workflows/main.yml b/library/compiler-builtins/libm/.github/workflows/main.yml
index 322043d85af3..f312e1f5e67c 100644
--- a/library/compiler-builtins/libm/.github/workflows/main.yml
+++ b/library/compiler-builtins/libm/.github/workflows/main.yml
@@ -41,7 +41,7 @@ jobs:
     steps:
     - uses: actions/checkout@master
     - name: Install Rust
-      run: rustup update stable && rustup default stable && rustup component add rustfmt
+      run: rustup update nightly && rustup default nightly && rustup component add rustfmt
     - run: cargo fmt -- --check
 
   wasm:
diff --git a/library/compiler-builtins/libm/.rustfmt.toml b/library/compiler-builtins/libm/.rustfmt.toml
new file mode 100644
index 000000000000..c73bb9301e34
--- /dev/null
+++ b/library/compiler-builtins/libm/.rustfmt.toml
@@ -0,0 +1,5 @@
+# This matches rustc
+style_edition = "2024"
+use_small_heuristics = "Max"
+group_imports = "StdExternalCrate"
+imports_granularity = "Module"