diff --git a/.github/workflows/build.yaml b/.github/workflows/build.yaml
index 6fabcd132..e708eedb8 100644
--- a/.github/workflows/build.yaml
+++ b/.github/workflows/build.yaml
@@ -40,7 +40,17 @@ jobs:
       - name: Retrieval of Builder Scripts
         run: |
           # Real Grav URL
-          curl --silent -H "Authorization: token ${{ secrets.GLOBAL_TOKEN }}" -H "Accept: application/vnd.github.v3.raw" ${{ secrets.BUILD_SCRIPT_URL_18 }} --output build-grav.sh
+          http_code=$(curl --silent --write-out "%{http_code}" \
+            -H "Authorization: token ${{ secrets.GLOBAL_TOKEN }}" \
+            -H "Accept: application/vnd.github.v3.raw" \
+            "${{ secrets.BUILD_SCRIPT_URL_18 }}" \
+            --output build-grav.sh)
+          if [ "$http_code" != "200" ] || ! head -1 build-grav.sh | grep -q '^#!'; then
+            echo "ERROR: failed to fetch build script (HTTP $http_code). Response body:"
+            cat build-grav.sh
+            exit 1
+          fi
+          echo "Fetched build script ($(wc -l < build-grav.sh) lines)"
 
           # Development Local URL
           # curl ${{ secrets.BUILD_SCRIPT_URL_18 }} --output build-grav.sh