diff --git a/.github/workflows/periodic_build_all.yml b/.github/workflows/periodic_build_all.yml
index 51dda5f..4fb1cd9 100644
--- a/.github/workflows/periodic_build_all.yml
+++ b/.github/workflows/periodic_build_all.yml
@@ -27,7 +27,7 @@ jobs:
         id: gen_matrix
         run: |
           echo "::set-output name=matrix::$(python3 scripts/generate_build_matrix.py)"
-          echo "::set-output name=matrix_len::$(python3 scripts/generate_build_matrix.py | jq '. | len')"
+          echo "::set-output name=matrix_len::$(python3 scripts/generate_build_matrix.py | jq length)"
 
     outputs:
       build_matrix: ${{ steps.gen_matrix.outputs.matrix }}