diff --git a/middleware/withShop.js b/middleware/withShop.js
index 4f69cbe..a218a3e 100644
--- a/middleware/withShop.js
+++ b/middleware/withShop.js
@@ -1,18 +1,27 @@
 module.exports = function withShop({ authBaseUrl } = {}) {
   return function verifyRequest(request, response, next) {
-    const { query: { shop }, session, baseUrl } = request;
+    const { query = {}, session = {}, baseUrl } = request;
+    const { accessToken } = session;
+    const shop = getShopFromReferrer(request.get('referer')) || query.shop;
 
-    if (session && session.accessToken) {
+    if (accessToken && session.shop === shop) {
       next();
       return;
     }
 
     if (shop) {
-      response.redirect(`${authBaseUrl || baseUrl}/auth?shop=${shop}`);
+      response.redirect(`${authBaseUrl || baseUrl}/auth/shopify?shop=${shop}`);
       return;
     }
 
     response.redirect('/install');
-    return;
   };
+
+  function getShopFromReferrer(referrer) {
+    if (!referrer) {
+      return;
+    }
+    const result = referrer.match(/shop=([^&]+)/);
+    return result && result[1];
+  }
 };