diff --git a/.github/workflows/msys2-build.yml b/.github/workflows/msys2-build.yml
index 1aaf56543..c2992e63b 100644
--- a/.github/workflows/msys2-build.yml
+++ b/.github/workflows/msys2-build.yml
@@ -34,6 +34,7 @@ jobs:
     steps:
     - name: Get current date as package key
       id: pkg_key
+      shell: bash
       run: echo "::set-output name=key::$(date +'%W')"
 
     - name: Checkout repository