--- a/toolkit/components/telemetry/TelemetrySession.jsm
+++ b/toolkit/components/telemetry/TelemetrySession.jsm
@@ -1971,17 +1971,17 @@ var Impl = {
       break;
     case TOPIC_CYCLE_COLLECTOR_BEGIN:
       let now = new Date();
       if (!gLastMemoryPoll
           || (TELEMETRY_INTERVAL <= now - gLastMemoryPoll)) {
         gLastMemoryPoll = now;
 
         this._log.trace("Dispatching idle gatherMemory task");
-        Services.tm.mainThread.idleDispatch(() => {
+        Services.tm.idleDispatchToMainThread(() => {
           this._log.trace("Running idle gatherMemory task");
           this.gatherMemory();
           return true;
         });
       }
       break;
     case "xul-window-visible":
       this.removeObserver("xul-window-visible");