diff --git a/lib/delphi/src/Thrift.Protocol.pas b/lib/delphi/src/Thrift.Protocol.pas
index 5618d6f..7ae8e34 100644
--- a/lib/delphi/src/Thrift.Protocol.pas
+++ b/lib/delphi/src/Thrift.Protocol.pas
@@ -530,7 +530,7 @@
 
   IProcessor = interface
     ['{7BAE92A5-46DA-4F13-B6EA-0EABE233EE5F}']
-    function Process( const iprot :IProtocol; const oprot: IProtocol; const events : IProcessorEvents): Boolean;
+    function Process( const iprot :IProtocol; const oprot: IProtocol; const events : IProcessorEvents = nil): Boolean;
   end;