diff --git a/.github/workflows/size.yml b/.github/workflows/size.yml
index e002e1593e..a6641244ad 100644
--- a/.github/workflows/size.yml
+++ b/.github/workflows/size.yml
@@ -1,5 +1,10 @@
 name: size
-on: [pull_request]
+on:
+  pull_request:
+    branches:
+      - master
+permissions:
+  pull-requests: write
 jobs:
   size:
     runs-on: ubuntu-latest