1 files changed, 9 insertions, 2 deletions

diff --git a/src/vm.c b/src/vm.c
index 9cc29ed5a..5d2e04383 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -717,15 +717,22 @@ argnum_error(mrb_state *mrb, mrb_int num)
 {
   mrb_value exc;
   mrb_value str;
+  mrb_int argc = mrb->c->ci->argc;
 
+  if (argc < 0) {
+    mrb_value args = mrb->c->stack[1];
+    if (mrb_array_p(args)) {
+      argc = RARRAY_LEN(args);
+    }
+  }
   if (mrb->c->ci->mid) {
     str = mrb_format(mrb, "'%S': wrong number of arguments (%S for %S)",
                   mrb_sym2str(mrb, mrb->c->ci->mid),
-                  mrb_fixnum_value(mrb->c->ci->argc), mrb_fixnum_value(num));
+                  mrb_fixnum_value(argc), mrb_fixnum_value(num));
   }
   else {
     str = mrb_format(mrb, "wrong number of arguments (%S for %S)",
-                  mrb_fixnum_value(mrb->c->ci->argc), mrb_fixnum_value(num));
+                     mrb_fixnum_value(argc), mrb_fixnum_value(num));
   }
   exc = mrb_exc_new_str(mrb, E_ARGUMENT_ERROR, str);
   mrb_exc_set(mrb, exc);