diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
index 87992008..cbb1bdc4 100644
--- a/.github/workflows/lint.yml
+++ b/.github/workflows/lint.yml
@@ -19,9 +19,15 @@ jobs:
 
     - name: Install clang-format
       run: |
-        wget https://apt.llvm.org/llvm.sh
-        sudo bash ./llvm.sh 21
-        sudo apt install clang-format-21
+        sudo install -D -m 0644 support/llvm-snapshot.gpg.key \
+          /etc/apt/keyrings/apt.llvm.org.asc
+        codename=$(lsb_release -cs)
+        echo "deb [signed-by=/etc/apt/keyrings/apt.llvm.org.asc]" \
+             "https://apt.llvm.org/$codename/" \
+             "llvm-toolchain-$codename-21 main" \
+          | sudo tee /etc/apt/sources.list.d/llvm.list
+        sudo apt-get update
+        sudo apt-get install -y clang-format-21
 
     - name: Run clang-format
       run: |
diff --git a/support/llvm-snapshot.gpg.key b/support/llvm-snapshot.gpg.key
new file mode 100644
index 00000000..27f27e13
--- /dev/null
+++ b/support/llvm-snapshot.gpg.key
@@ -0,0 +1,52 @@
+-----BEGIN PGP PUBLIC KEY BLOCK-----
+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+=/NY6
+-----END PGP PUBLIC KEY BLOCK-----