diff --git a/.github/workflows/firmware.yml b/.github/workflows/firmware.yml
index 9a094d3..8addfce 100644
--- a/.github/workflows/firmware.yml
+++ b/.github/workflows/firmware.yml
@@ -55,6 +55,11 @@ jobs:
       - name: Install build dependencies
         run: |
           sudo -E ./scripts/install_build_dependencies.sh
+      - name: Update GITHUB_SHA env
+        run: |
+          if [ "$GITHUB_EVENT_NAME" == "pull_request" ]; then
+              GITHUB_SHA=$(cat $GITHUB_EVENT_PATH | jq -r .pull_request.head.sha) # GITHUB_SHA is the merge SHA, not the head commit SHA in a PR, replace it.
+          fi
       - name: build target ${{ matrix.target }}
         id: compile
         run: |