diff --git a/npm/npm-test/action.yaml b/npm/npm-test/action.yaml
index 61705db..343ffcc 100644
--- a/npm/npm-test/action.yaml
+++ b/npm/npm-test/action.yaml
@@ -65,11 +65,13 @@ runs:
   - name: "Configure npm authentication"
     if: ${{ inputs.registries && inputs.apiKeys }}
     run: |
+      DEFAULT_REGISTRY="https://registry.npmjs.org"
+      DEFAULT_API_KEY="none"
       REGISTRIES="${{ inputs.registries }}"
       API_KEYS="${{ inputs.apiKeys }}"
       if [ "${{ inputs.useDefaultRegistry }}" == "true" ]; then
-        REGISTRIES=$(printf '%s\n%s' 'https://registry.npmjs.org' "$REGISTRIES")
-        API_KEYS=$(printf '%s\n%s' 'none' "$API_KEYS")
+        REGISTRIES=$(printf '%s\n%s' "$DEFAULT_REGISTRY" "$REGISTRIES")
+        API_KEYS=$(printf '%s\n%s' "$DEFAULT_API_KEY" "$API_KEYS")
       fi
       bash "${{ github.action_path }}/configure-auth.sh" add "$REGISTRIES" "$API_KEYS"
     working-directory: ${{ inputs.workingDirectory }}