diff --git a/py/objfun.c b/py/objfun.c
index 3fd25fb224..fd51dd589d 100644
--- a/py/objfun.c
+++ b/py/objfun.c
@@ -409,17 +409,15 @@ STATIC mp_obj_t fun_viper_call(mp_obj_t self_in, size_t n_args, size_t n_kw, con
         ret = ((viper_fun_2_t)fun)(mp_convert_obj_to_native(args[0], self->type_sig >> 4), mp_convert_obj_to_native(args[1], self->type_sig >> 8));
     } else if (n_args == 3) {
         ret = ((viper_fun_3_t)fun)(mp_convert_obj_to_native(args[0], self->type_sig >> 4), mp_convert_obj_to_native(args[1], self->type_sig >> 8), mp_convert_obj_to_native(args[2], self->type_sig >> 12));
-    } else if (n_args == 4) {
+    } else {
+        // compiler allows at most 4 arguments
+        assert(n_args == 4);
         ret = ((viper_fun_4_t)fun)(
             mp_convert_obj_to_native(args[0], self->type_sig >> 4),
             mp_convert_obj_to_native(args[1], self->type_sig >> 8),
             mp_convert_obj_to_native(args[2], self->type_sig >> 12),
             mp_convert_obj_to_native(args[3], self->type_sig >> 16)
         );
-    } else {
-        // TODO 5 or more arguments not supported for viper call
-        assert(0);
-        ret = 0;
     }
 
     return mp_convert_native_to_obj(ret, self->type_sig);