diff --git a/Jenkinsfile b/Jenkinsfile
index 52fba9c..7b8202a 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -6,6 +6,17 @@ pipeline {
     }
     triggers { cron(env.BRANCH_NAME ==~ /^main$/ ? 'H H(0-6) 1 * *' : '') }
     stages {
+        stage('Quality Checks') {
+            agent { label 'my127ws' }
+            steps {
+                sh './quality.sh'
+            }
+            post {
+                always {
+                    cleanWs()
+                }
+            }
+        }
         stage('Matrix') {
             matrix {
                 axes {
diff --git a/quality.sh b/quality.sh
new file mode 100755
index 0000000..125599e
--- /dev/null
+++ b/quality.sh
@@ -0,0 +1,12 @@
+#!/bin/bash
+set -e -o pipefail
+
+if ! docker image ls -a --format '{{ print .Repository ":" .Tag }}' | grep -q koalaman/shellcheck-alpine:stable; then
+  docker pull koalaman/shellcheck-alpine:stable
+fi
+
+run_shellcheck()
+{
+  docker run --rm --volume "$(pwd):/app" koalaman/shellcheck-alpine:stable /bin/sh -c 'find /app -type f ! -path "*/.git/*" ! -name "*.orig" -and \( -name "*.sh" -or -perm -0111 \) -print -exec shellcheck --exclude SC1008,SC1091 {} +'
+}
+run_shellcheck
diff --git a/test.extensions.sh b/test.extensions.sh
index 375c303..75bb99e 100755
--- a/test.extensions.sh
+++ b/test.extensions.sh
@@ -55,5 +55,5 @@ for extension in extensions/*; do
 done
 
 after="$(php -m)$(php -v)"
-echo "After: $after\nDiff:"
+printf "After: %s\nDiff:" "$after"
 diff -u <(echo "$before") <(echo "$after") || true