1 files changed, 5 insertions, 4 deletions
diff --git a/src/gc.c b/src/gc.c
index 1d7a8627f..0ba6e3e76 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -261,12 +261,13 @@ mrb_obj_alloc(mrb_state *mrb, enum mrb_vtype ttype, struct RClass *cls)
   }
 
   mrb->live++;
-  mrb->arena[mrb->arena_idx++] = p;
-  memset(p, 0, sizeof(RVALUE));
-  if (mrb->arena_idx >= MRB_ARENA_SIZE) {
+  if (mrb->arena_idx > MRB_ARENA_SIZE) {
     /* arena overflow error */
-    mrb_raise(mrb, E_TYPE_ERROR, "arena overflow error");
+    mrb->arena_idx = MRB_ARENA_SIZE - 2; /* force room in arena */
+    mrb_raise(mrb, mrb->eRuntimeError_class, "arena overflow error");
   }
+  mrb->arena[mrb->arena_idx++] = p;
+  memset(p, 0, sizeof(RVALUE));
   p->tt = ttype;
   p->c = cls;
   paint_partial_white(mrb, p);