diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 8e75a2f..6bd18ab 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -17,6 +17,11 @@ jobs:
             - name: Checkout repository
               uses: actions/checkout@c85c95e3d7251135ab7dc9ce3241c5835cc595a9 # v3.5.3
 
+            - name: Install Subversion
+              run: |
+                sudo apt-get update
+                sudo apt-get install -y subversion
+
             # Required for old theme build step.
             - name: Checkout wporg CSS
               run: |
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 23b9a93..1ccd666 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -17,6 +17,11 @@ jobs:
       with:
         fetch-depth: 0
 
+    - name: Install Subversion
+      run: |
+        sudo apt-get update
+        sudo apt-get install -y subversion
+
     - name: Get Composer cache directory
       id: composer-cache
       run: echo "::set-output name=dir::$(composer config cache-files-dir)"
@@ -73,6 +78,11 @@ jobs:
     steps:
     - uses: actions/checkout@v2
 
+    - name: Install Subversion
+      run: |
+        sudo apt-get update
+        sudo apt-get install -y subversion
+
     - name: Get Composer cache directory
       id: composer-cache
       run: echo "::set-output name=dir::$(composer config cache-files-dir)"