diff --git a/extlib/benz/gc.c b/extlib/benz/gc.c
index 300b131f..18906f40 100644
--- a/extlib/benz/gc.c
+++ b/extlib/benz/gc.c
@@ -696,6 +696,15 @@ pic_gc(pic_state *pic)
   gc_sweep_phase(pic);
 }
 
+void *
+pic_alloca(pic_state *pic, size_t n)
+{
+  static const pic_data_type t = { "pic_alloca", pic_free, 0 };
+
+  /* TODO: optimize */
+  return pic_data_alloc(pic, &t, pic_malloc(pic, n))->data;
+}
+
 struct pic_object *
 pic_obj_alloc_unsafe(pic_state *pic, size_t size, enum pic_tt tt)
 {
diff --git a/extlib/benz/include/picrin.h b/extlib/benz/include/picrin.h
index 93322e57..99ab5562 100644
--- a/extlib/benz/include/picrin.h
+++ b/extlib/benz/include/picrin.h
@@ -137,6 +137,7 @@ void pic_free(pic_state *, void *);
 
 typedef pic_value (*pic_func_t)(pic_state *);
 
+void *pic_alloca(pic_state *, size_t);
 pic_value pic_gc_protect(pic_state *, pic_value);
 size_t pic_gc_arena_preserve(pic_state *);
 void pic_gc_arena_restore(pic_state *, size_t);