diff --git a/src/ex_cmds2.c b/src/ex_cmds2.c
index 8bab853..18c438c 100644
--- a/src/ex_cmds2.c
+++ b/src/ex_cmds2.c
@@ -325,7 +325,7 @@
     argv[0].vval.v_number = (varnumber_T)timer->tr_id;
     argv[1].v_type = VAR_UNKNOWN;
 
-    call_func(timer->tr_callback, (int)STRLEN(timer->tr_callback),
+    call_func(timer->tr_callback, -1,
 			&rettv, 1, argv, NULL, 0L, 0L, &dummy, TRUE,
 			timer->tr_partial, NULL);
     clear_tv(&rettv);