diff --git a/README.md b/README.md
index d54ee9e..5e9664a 100644
--- a/README.md
+++ b/README.md
@@ -17,6 +17,19 @@ Requires [Node](https://nodejs.org/en/) version 8.9 or above.
 npm install --save-dev start-server-and-test
 ```
 
+## Upgrade
+
+### v1 to v2
+
+If you are using just the port number, and the resolved URL `localhost:xxxx` no longer works, use the explicit `http://localhost:xxxx` instead
+
+```
+# v1
+$ npx start-test 3000
+# v2
+$ npx start-test http://localhost:3000
+```
+
 ## Use
 
 This command is meant to be used with NPM script commands. If you have a "start server", and "test" script names for example, you can start the server, wait for a url to respond, then run tests. When the test process exits, the server is shut down.
diff --git a/src/utils.js b/src/utils.js
index 94c0037..abd1a69 100644
--- a/src/utils.js
+++ b/src/utils.js
@@ -214,7 +214,11 @@ const normalizeUrl = input => {
       return s
     }
 
-    if (s.startsWith('localhost') || s.startsWith('127.0.0.1') || s.startsWith('0.0.0.0')) {
+    if (
+      s.startsWith('localhost') ||
+      s.startsWith('127.0.0.1') ||
+      s.startsWith('0.0.0.0')
+    ) {
       return `http://${s}`
     }