diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 06549fc..d466ade 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -57,17 +57,24 @@ jobs:
 
       - name: Prepare Firefox source
         run: |
-          mkdir -p dist/firefox-source
-          rsync -a \
-            --exclude '.git/' \
-            --exclude '.github/' \
-            --exclude 'web-ext-artifacts/' \
-            --exclude 'manifest.chrome.json' \
-            --exclude 'background-chrome.js' \
-            --exclude 'background-service-worker.js' \
-            --exclude 'browser-api.js' \
-            --exclude 'scripts/' \
-            ./ dist/firefox-source/
+          python - <<'PY'
+          from pathlib import Path
+          import shutil
+          source = Path('.')
+          target = Path('dist/firefox-source')
+          excluded = {'.git', '.github', 'dist', 'web-ext-artifacts', 'scripts',
+                      'manifest.chrome.json', 'background-chrome.js',
+                      'background-service-worker.js', 'browser-api.js'}
+          target.mkdir(parents=True, exist_ok=True)
+          for item in source.iterdir():
+              if item.name in excluded:
+                  continue
+              destination = target / item.name
+              if item.is_dir():
+                  shutil.copytree(item, destination, dirs_exist_ok=True)
+              else:
+                  shutil.copy2(item, destination)
+          PY
 
       - name: Build Firefox package
         run: |
@@ -124,17 +131,24 @@ jobs:
       - name: Set up Firefox signing tools
         run: |
           npm install --global web-ext
-          mkdir -p dist/firefox-source
-          rsync -a \
-            --exclude '.git/' \
-            --exclude '.github/' \
-            --exclude 'web-ext-artifacts/' \
-            --exclude 'manifest.chrome.json' \
-            --exclude 'background-chrome.js' \
-            --exclude 'background-service-worker.js' \
-            --exclude 'browser-api.js' \
-            --exclude 'scripts/' \
-            ./ dist/firefox-source/
+          python - <<'PY'
+          from pathlib import Path
+          import shutil
+          source = Path('.')
+          target = Path('dist/firefox-source')
+          excluded = {'.git', '.github', 'dist', 'web-ext-artifacts', 'scripts',
+                      'manifest.chrome.json', 'background-chrome.js',
+                      'background-service-worker.js', 'browser-api.js'}
+          target.mkdir(parents=True, exist_ok=True)
+          for item in source.iterdir():
+              if item.name in excluded:
+                  continue
+              destination = target / item.name
+              if item.is_dir():
+                  shutil.copytree(item, destination, dirs_exist_ok=True)
+              else:
+                  shutil.copy2(item, destination)
+          PY
 
       - name: Sign and submit Firefox package to AMO
         run: |