diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 2f80b9b..4a47b82 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -19,18 +19,27 @@ jobs:
     - uses: actions/checkout@v4
     - name: Mark repo safe in non-fake global config
       run: git config --global --add safe.directory "${GITHUB_WORKSPACE}"
-    - name: Setup swift-format
+    - name: Clone swift-format
       run: |
         cd ..
         VERSION=510.1.0
         git clone https://github.com/apple/swift-format.git
         cd swift-format
         git checkout "tags/$VERSION"
+        cd "${GITHUB_WORKSPACE}"
+    - name: Cache swift-format
+      uses: actions/cache@v4
+      with:
+        path: .build
+        key: ${{ runner.os }}-ci-spm-${{ hashFiles('../swift-format/Package.swift') }}
+        restore-keys: ${{ runner.os }}-ci-spm-
+    - name: Setup swift-format
+      run: |
+        cd ../swift-format
         swift build -c release
+        export SWIFTFORMAT_BIN=$(pwd)/.build/release/swift-format"
         cd "${GITHUB_WORKSPACE}"
     - name: Run soundness
-      env:
-        SWIFTFORMAT_BIN: "${GITHUB_WORKSPACE}/../swift-format/.build/release/swift-format"
       run: |
         scripts/soundness.sh
         exit $(git status --porcelain | wc -l)