diff --git a/autobahn/autobahn.d.ts b/autobahn/autobahn.d.ts
index 97837b52d0..7fd344f727 100644
--- a/autobahn/autobahn.d.ts
+++ b/autobahn/autobahn.d.ts
@@ -45,7 +45,7 @@ declare namespace autobahn {
 
     interface IInvocation {
         caller?: number;
-        progress?: boolean;
+        progress?: (args : any[], kwargs : any) => void;
         procedure: string;
     }