diff --git a/mrbgems/mruby-bin-mirb/tools/mirb/mirb.c b/mrbgems/mruby-bin-mirb/tools/mirb/mirb.c
index 7622aacd1..590bc13b5 100644
--- a/mrbgems/mruby-bin-mirb/tools/mirb/mirb.c
+++ b/mrbgems/mruby-bin-mirb/tools/mirb/mirb.c
@@ -477,6 +477,8 @@ main(int argc, char **argv)
   mirb_editor editor;
   mirb_check_data check_data;
   mrb_bool use_editor = FALSE;
+
+  memset(&editor, 0, sizeof(editor));
   mrb_ccontext *cxt;
   struct mrb_parser_state *parser;
   mrb_state *mrb;