diff --git a/.github/workflows/cs.yml b/.github/workflows/cs.yml
index 8450e8b..435e65f 100644
--- a/.github/workflows/cs.yml
+++ b/.github/workflows/cs.yml
@@ -36,6 +36,9 @@ jobs:
       # @link https://github.com/marketplace/actions/install-composer-dependencies
       - name: Install Composer dependencies
         uses: "ramsey/composer-install@v2"
+        with:
+          # Bust the cache at least once a month - output format: YYYY-MM-DD.
+          custom-cache-suffix: $(date -u -d "-0 month -$(($(date +%d)-1)) days" "+%F")
 
       # Check the code-style consistency of the PHP files.
       - name: Check PHP code style
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 103045c..9105a5b 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -136,6 +136,9 @@ jobs:
       - name: Install Composer dependencies - normal
         if: ${{ steps.composer_toggle.outputs.TYPE == '1' || steps.composer_toggle.outputs.TYPE == '3' }}
         uses: "ramsey/composer-install@v2"
+        with:
+          # Bust the cache at least once a month - output format: YYYY-MM-DD.
+          custom-cache-suffix: $(date -u -d "-0 month -$(($(date +%d)-1)) days" "+%F")
 
       # For PHP 8.0 and above on WP 5.2 - 5.8, we need to install with ignore platform reqs as not all dependencies allow it.
       - name: Install Composer dependencies with ignore platform reqs
@@ -143,6 +146,7 @@ jobs:
         uses: "ramsey/composer-install@v2"
         with:
           composer-options: --ignore-platform-req=php
+          custom-cache-suffix: $(date -u -d "-0 month -$(($(date +%d)-1)) days" "+%F")
 
       - name: Run the unit tests - single site
         run: vendor/bin/phpunit