Don't try to fetch FxA migration sentinel from non-supporting server.

This resolves #522.

1 files changed, 2 insertions, 1 deletions

diff --git a/services/sync/modules/service.js b/services/sync/modules/service.js
index f8c64b0fa..32e047f53 100644
--- a/services/sync/modules/service.js
+++ b/services/sync/modules/service.js
@@ -1338,9 +1338,10 @@ Sync11Service.prototype = {
       // We successfully synchronized.
       // Check if the identity wants to pre-fetch a migration sentinel from
       // the server.
+      // Only supported by Sync server API level 2+
       // If we have no clusterURL, we are probably doing a node reassignment
       // so don't attempt to get it in that case.
-      if (this.clusterURL) {
+      if (Svc.Prefs.get("APILevel") >= 2 && this.clusterURL) {
         this.identity.prefetchMigrationSentinel(this);
       }