diff --git a/packages/pwa-utils/index.js b/packages/pwa-utils/index.js
index 4cb89a0b..9c51ef06 100755
--- a/packages/pwa-utils/index.js
+++ b/packages/pwa-utils/index.js
@@ -31,7 +31,7 @@ function getRouteParams (options) {
 }
 
 function startCase (str) {
-  return str[0].toUpperCase() + str.substr(1)
+  return typeof str === 'string' ? str[0].toUpperCase() + str.substr(1) : str
 }
 
 module.exports = {