diff --git a/.github/workflows/mac.yml b/.github/workflows/mac.yml
index e719ccd0..b3f1860f 100644
--- a/.github/workflows/mac.yml
+++ b/.github/workflows/mac.yml
@@ -6,6 +6,7 @@ jobs:
 
   tests:
     runs-on: self-hosted
+    if: github.repository == 'stfc/janus-core'
     timeout-minutes: 30
     strategy:
       matrix: