diff --git a/content/install-hook-usercss.js b/content/install-hook-usercss.js
index 622b3143..c88c13ea 100644
--- a/content/install-hook-usercss.js
+++ b/content/install-hook-usercss.js
@@ -54,6 +54,12 @@
   }
 
   function fetchText(url) {
+    // XHR throws in Chrome 49
+    // FIXME: choose a correct version
+    // https://github.com/openstyles/stylus/issues/560
+    if (getChromeVersion() <= 49) {
+      return fetch(url).then(r => r.text());
+    }
     return new Promise((resolve, reject) => {
       // you can't use fetch in Chrome under 'file:' protocol
       const xhr = new XMLHttpRequest();
@@ -64,6 +70,11 @@
     });
   }
 
+  function getChromeVersion() {
+    const match = navigator.userAgent.match(/chrome\/(\d+)/i);
+    return match && Number(match[1]);
+  }
+
   function start() {
     timer = timer || setTimeout(check, DELAY);
   }