diff --git a/.github/workflows/pr-check.yml b/.github/workflows/pr-check.yml
index 0c7f89c..845e5d9 100644
--- a/.github/workflows/pr-check.yml
+++ b/.github/workflows/pr-check.yml
@@ -101,6 +101,10 @@ jobs:
             PR_THREAD_COUNT=$(gh api repos/$GH_REPO/pulls/$PR_NUM/comments \
                 --jq '[.[] | select(.position != null)] | length')
 
+            COMMIT_COUNT="(gh api repos/$GH_REPO/pulls/$PR_NUM --jq '.commits')"
+
+            CONTAINS_MASTER=$(gh api repos/$GH_REPO/pulls/$PR_NUM/commits --jq '.[1] | (.commit.author.email == "mclasen@redhat.com" and .commit.message == "Add some instructions")')
+
             BLOCKED=0
 
             comment_exists() {
@@ -140,6 +144,16 @@ jobs:
               fi
             }
 
+            if [ "$CONTAINS_MASTER" = "true" ]; then
+              echo "PR contains commits from master branch"
+              BLOCKED=1
+            fi
+
+            if [ "$CONTAINS_MASTER" = "true" ]; then
+              echo "PR contains commits from master branch"
+              BLOCKED=1
+            fi
+
             if [ "$EXIT_CODE" -ne 0 ]; then
               echo "PR title validation failed"
               BLOCKED=1
@@ -230,6 +244,16 @@ jobs:
 
             bot, build
           BUILD_START_COMMENT_PARTIAL: "Starting a test build of the submission"
+          REVIEW_COMMENT: |
+            This pull request is temporarily marked as blocked as some
+            automated checks failed on it. Please make sure the
+            following are items are done:
+
+            1. The title of the pull request is `Add $FLATPAK_ID`.
+            2. All [checklist items](https://github.com/flathub/flathub/blob/master/.github/pull_request_template.md)
+               in the pull request body are marked as complete.
+            3. The pull request does not contain commits from the `master`
+               branch of [this repository](https://github.com/flathub/flathub/commits/master/).
           REVIEW_COMMENT: >
             This pull request is temporarily marked as blocked as some
             automated checks failed on it. Please make sure the pull