diff --git a/action.yml b/action.yml
index 9c47d21d..8878f52a 100644
--- a/action.yml
+++ b/action.yml
@@ -194,6 +194,7 @@ runs:
       shell: bash
       env:
         GITHUB_WORKSPACE: ${{ github.workspace }}
+        GITHUB_BASE_REF: ${{ github.base_ref }}
         # INPUT_<VARIABLE_NAME> is not available in Composite run steps
         # https://docs.github.com/en/actions/creating-actions/metadata-syntax-for-github-actions#example-specifying-inputs
         INPUT_FILES_PATTERN_FILE: ${{ steps.glob.outputs.paths-output-file }}