diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 9b6e49beb..526219705 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -33,13 +33,20 @@ jobs:
         id: paths
         shell: bash
         env:
+          EVENT_NAME: ${{ github.event_name }}
           BASE_SHA: ${{ github.event_name == 'pull_request' && github.event.pull_request.base.sha || github.event.before }}
-          HEAD_SHA: ${{ github.sha }}
+          HEAD_SHA: ${{ github.event_name == 'pull_request' && github.event.pull_request.head.sha || github.sha }}
         run: |
           python_required=true
 
+          if [[ "$EVENT_NAME" == "pull_request" ]]; then
+            diff_range="${BASE_SHA}...${HEAD_SHA}"
+          else
+            diff_range="${BASE_SHA}..${HEAD_SHA}"
+          fi
+
           if git cat-file -e "${BASE_SHA}^{commit}" 2>/dev/null &&
-            changed_files="$(git diff --name-only --no-renames "$BASE_SHA" "$HEAD_SHA")" &&
+            changed_files="$(git diff --name-only --no-renames "$diff_range")" &&
             [[ -n "$changed_files" ]] &&
             ! grep -qvE '^(webui/|nanobot/channels/[^/]+/webui/|docs/)' <<< "$changed_files"; then
             python_required=false