diff --git a/.github/check-stylesheet.sh b/.github/check-stylesheet.sh
new file mode 100755
index 0000000000..f5984a24ce
--- /dev/null
+++ b/.github/check-stylesheet.sh
@@ -0,0 +1,18 @@
+#!/bin/bash
+#
+# This file is part of the phpBB Forum Software package.
+#
+# @copyright (c) phpBB Limited <https://www.phpbb.com>
+# @license GNU General Public License, version 2 (GPL-2.0)
+#
+# For full copyright and license information, please see
+# the docs/CREDITS.txt file.
+#
+set -e
+set +x
+
+sudo npm install -g > /dev/null
+npm install > /dev/null
+set -x
+node_modules/stylelint/bin/stylelint.js "phpBB/styles/prosilver/theme/*.css"
+node_modules/stylelint/bin/stylelint.js "phpBB/adm/style/*.css"
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index efb0934f0a..a4b05b3be3 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -80,6 +80,10 @@ jobs:
               run: |
                   .github/check-executable-files.sh ./
 
+            - name: Check stylesheets
+              run: |
+                  .github/check-stylesheet.sh
+
             - name: Check commit message
               env:
                   BRANCH: ${{ github.event.pull_request.base.sha }}