diff --git a/lib/utility.js b/lib/utility.js
index 8b52ee7..900bbd6 100644
--- a/lib/utility.js
+++ b/lib/utility.js
@@ -34,7 +34,7 @@ function callService(service, emitter, channel, callback) {
         emitter.once('error', reject);
         emitter.once(eventName, function (result) {
             emitter.removeListener('error', reject);
-            if (result.instanceOf('mtproto.type.Rpc_error')) {
+            if (typeof result !== 'boolean' && result.instanceOf('mtproto.type.Rpc_error')) {
                 reject(new Error(result.error_message));
             } else {
                 fulfill(result);