diff --git a/.github/workflows/ruby.yml b/.github/workflows/ruby.yml
index 403d6282..67321cbe 100644
--- a/.github/workflows/ruby.yml
+++ b/.github/workflows/ruby.yml
@@ -7,6 +7,9 @@ on:
     branches:
       - main
 
+permissions:
+  contents: read
+
 jobs:
   rubocop_and_matrix:
     runs-on: ubuntu-24.04