fix build

src/mod/endpoints/mod_loopback/mod_loopback.c

@@ -965,13 +965,13 @@ static switch_call_cause_t channel_outgoing_channel(switch_core_session_t *sessi
 				switch_channel_set_variable(channel, "loopback_app", app);
 
 				if (clone) {
-					switch_event_add_header(clone, SWITCH_STACK_BOTTOM, "loopback_app", app);
+					switch_event_add_header_string(clone, SWITCH_STACK_BOTTOM, "loopback_app", app);
 				}
 				
 				if (arg) {
 					switch_channel_set_variable(channel, "loopback_app_arg", arg);
 					if (clone) {
-						switch_event_add_header(clone, SWITCH_STACK_BOTTOM, "loopback_app_arg", arg);
+						switch_event_add_header_string(clone, SWITCH_STACK_BOTTOM, "loopback_app_arg", arg);
 					}
 				}