diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index c2af63f..73dd951 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -44,6 +44,10 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@v2
 
+      - name: Install Composer (macOS)
+        if: startsWith(runner.os, 'macOS')
+        run: curl -sS https://getcomposer.org/installer | php -- --install-dir=/usr/local/bin --filename=composer
+
       - name: Determine composer cache directory
         id: determine-composer-cache-directory
         run: 'echo "::set-output name=directory::$(composer config cache-dir)"'