diff --git a/.github/workflows/size-label.yml b/.github/workflows/size-label.yml
index b0118ca..64bf2e7 100644
--- a/.github/workflows/size-label.yml
+++ b/.github/workflows/size-label.yml
@@ -1,5 +1,7 @@
 name: Label size of PRs 
-on: pull_request
+on:
+  pull_request_target:
+    types: [opened, reopened, synchronize]
 jobs:
   size-label:
     runs-on: ubuntu-latest