diff --git a/background/update.js b/background/update.js
index 59268a14..c4ae8d5a 100644
--- a/background/update.js
+++ b/background/update.js
@@ -157,7 +157,7 @@
         // USO can't handle POST requests for style json
         return download(style.updateUrl, {body: null})
           // USO may not provide a correctly updated originalMd5 (#555)
-          .then(text => Object.assign(tryJSONparse(text), {originalMd5: md5}));
+          .then(text => Object.assign(tryJSONparse(text || '{}'), {originalMd5: md5}));
       });
     }