use mrb_str_buf_new to create a buffer to be used by mrb_str_buf_cat

1 files changed, 2 insertions, 1 deletions

diff --git a/src/vm.c b/src/vm.c
index 5a03595d0..2e92852bf 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -468,7 +468,8 @@ localjump_error(mrb_state *mrb, localjump_error_kind kind)
   mrb_value msg;
   mrb_value exc;
 
-  msg = mrb_str_new(mrb, lead, sizeof(lead) - 1);
+  msg = mrb_str_buf_new(mrb, sizeof(lead) + 7);
+  mrb_str_buf_cat(mrb, msg, lead, sizeof(lead) - 1);
   mrb_str_buf_cat(mrb, msg, kind_str[kind], kind_str_len[kind]);
   exc = mrb_exc_new3(mrb, E_LOCALJUMP_ERROR, msg);
   mrb->exc = (struct RObject*)mrb_object(exc);