diff --git a/ext/win32/lib/win32/resolv9x.rb b/ext/win32/lib/win32/resolv9x.rb
index 1045bb2e09..a409d59c0c 100644
--- a/ext/win32/lib/win32/resolv9x.rb
+++ b/ext/win32/lib/win32/resolv9x.rb
@@ -141,7 +141,7 @@ module Win32
         extend Importer
         dlload "wsock32.dll"
       end
-      WsControl = WSock32.extern "int WsControl(int, int, void *, void *, void *, void *", :stdcall
+      WsControl = WSock32.extern "int WsControl(int, int, void *, void *, void *, void *)", :stdcall
       WSAGetLastError = WSock32.extern "int WSAGetLastError(void)", :stdcall
 
       MAX_TDI_ENTITIES = 512