diff --git a/.github/workflows/smoke.yaml b/.github/workflows/smoke.yaml
index 7432f235..b9703774 100644
--- a/.github/workflows/smoke.yaml
+++ b/.github/workflows/smoke.yaml
@@ -4,11 +4,7 @@ name: "Run smoke tests via Tox::pytest (python 3.11)"
 # These tests will be long running and require accelerated hardware.
 
 on:
-  workflow_dispatch:
-    inputs:
-      branch:
-        type: string
-        default: main
+  workflow_dispatch: {}
   # using this rather than pull_request because this workflow
   # needs to run in the context of the base branch (main) and
   # access the repo's secrets to start the AWS instances.
@@ -115,7 +111,13 @@ jobs:
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
         with:
           fetch-depth: 0
-          ref: ${{inputs.branch}}
+
+      - name: "Fetch and checkout PR"
+        # Needed because this workflow runs on pull_request_target which runs on the base branch (e.g. main)
+        if: ${{ github.event_name == 'pull_request_target'}}
+        run: |
+          git fetch origin pull/${{ github.event.number }}/head:pr-${{ github.event.number }}
+          git checkout pr-${{ github.event.number }}
 
       - name: Run smoke tests
         uses: ./.github/actions/run-smoke