diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 217afad46..34fb527d1 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -33,7 +33,7 @@ jobs:
       if: matrix.os != 'ARM64'
     - run: |
           cd ihp-boilerplate
-          php ../.github/patch-flakes.php ${{ github.ref }} ${{ github.event.repository.full_name }} ${{ github.sha }}
+          ix-shell -p php --run "php ../.github/patch-flakes.php ${{ github.ref }} ${{ github.event.repository.full_name }} ${{ github.sha }}"
           cat flake.nix
           mv Makefile Makefile.old
           echo 'GHC_OPTIONS+= -rtsopts=all\n.SHELLFLAGS := -eu -o pipefail -c\n\n'|cat - Makefile.old > Makefile