diff --git a/.github/workflows/verify-fmt.yml b/.github/workflows/verify-fmt.yml
new file mode 100644
index 0000000..2332d6d
--- /dev/null
+++ b/.github/workflows/verify-fmt.yml
@@ -0,0 +1,17 @@
+name: Verify Format
+
+on:
+  pull_request:
+    branches: [main]
+
+jobs:
+  Patch:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Verify domain.txt
+        run: |
+          ./hack/verify-fmt.sh domain.txt || { echo "Please run './hack/fmt.sh domain.txt'"; exit 1; }
+      - name: Verify mirror.txt
+        run: |
+          ./hack/verify-fmt.sh mirror.txt || { echo "Please run './hack/fmt.sh mirror.txt'"; exit 1; }
diff --git a/hack/fmt.sh b/hack/fmt.sh
index 0a78971..4689ca0 100755
--- a/hack/fmt.sh
+++ b/hack/fmt.sh
@@ -1,3 +1,3 @@
 #!/usr/bin/env bash
 
-cat $1 | sort | tac > $1.tmp && mv $1.tmp $1
+cat $1 | sort -u | grep -v '^$' > $1.tmp && mv $1.tmp $1
diff --git a/hack/verify-fmt.sh b/hack/verify-fmt.sh
new file mode 100755
index 0000000..edfd679
--- /dev/null
+++ b/hack/verify-fmt.sh
@@ -0,0 +1,7 @@
+#!/usr/bin/env bash
+
+cp $1 $1.bak
+./hack/fmt.sh $1
+
+diff -c $1 $1.bak
+rm $1.bak
diff --git a/mirror.txt b/mirror.txt
index 4ad2f98..dd44d2a 100644
--- a/mirror.txt
+++ b/mirror.txt
@@ -213,4 +213,4 @@ quay.io/prometheus/alertmanager
 quay.io/prometheus/node-exporter
 quay.io/prometheus/prometheus
 quay.io/tigera/operator
-rocks.canonical.com/mariadb/server
\ No newline at end of file
+rocks.canonical.com/mariadb/server