diff --git a/.woodpecker.yml b/.woodpecker.yml
index 2aab2ed..3a5c125 100644
--- a/.woodpecker.yml
+++ b/.woodpecker.yml
@@ -11,7 +11,7 @@ steps:
       - git config --local user.name "$(git log --format=%an | head -n 1)"
       - git config --local user.email "$(git log --format=%ae | head -n 1)"
       - shasum=$(sha256sum install.sh)
-      - oldShasum=$(grep -oP "^[[:alnum:]]{64}" README.md)
+      - oldShasum=$(perl -ne 'print if /^[[:alnum:]]{64}/' README.md)
       - if ! [ "$shasum" = "$oldShasum" ]; then sed -i "s/$oldShasum/$shasum/" README.md; fi
       - if [ -z "$(git status --porcelain)" ]; then exit 0; fi
       - git add README.md