diff --git a/src/class.c b/src/class.c
index 44121bce6..3268dc7d3 100644
--- a/src/class.c
+++ b/src/class.c
@@ -569,7 +569,7 @@ mrb_get_args(mrb_state *mrb, const char *format, ...)
   char c;
   int i = 0;
   va_list ap;
-  int argc = mrb->c->ci->argc;
+  mrb_int argc = mrb->c->ci->argc;
   int arg_i = 0;
   mrb_value *array_argv;
   mrb_bool opt = FALSE;