diff --git a/libs/surfaces/mackie/mackie_control_protocol.cc b/libs/surfaces/mackie/mackie_control_protocol.cc
index c975ede7c1..665f58f02e 100644
--- a/libs/surfaces/mackie/mackie_control_protocol.cc
+++ b/libs/surfaces/mackie/mackie_control_protocol.cc
@@ -942,7 +942,7 @@ MackieControlProtocol::create_surfaces ()
 				ipm->mcp = this;
 				ipm->port = &input_port;
 
-				g_source_set_callback (surface->input_source, G_SOURCE_FUNC (ipmidi_input_handler), ipm, NULL);
+				g_source_set_callback (surface->input_source, (GSourceFunc) ipmidi_input_handler, ipm, NULL);
 				g_source_attach (surface->input_source, main_loop()->get_context()->gobj());
 			}
 		}