diff --git a/extlib/benz/gc.c b/extlib/benz/gc.c
index 39c94351..2fc69b74 100644
--- a/extlib/benz/gc.c
+++ b/extlib/benz/gc.c
@@ -57,24 +57,24 @@ heap_init(struct pic_heap *heap)
 }
 
 struct pic_heap *
-pic_heap_open()
+pic_heap_open(pic_state *pic)
 {
   struct pic_heap *heap;
 
-  heap = (struct pic_heap *)calloc(1, sizeof(struct pic_heap));
+  heap = pic_calloc(pic, 1, sizeof(struct pic_heap));
   heap_init(heap);
   return heap;
 }
 
 void
-pic_heap_close(struct pic_heap *heap)
+pic_heap_close(pic_state *pic, struct pic_heap *heap)
 {
   struct heap_page *page;
 
   while (heap->pages) {
     page = heap->pages;
     heap->pages = heap->pages->next;
-    free(page);
+    pic_free(pic, page);
   }
 }
 
diff --git a/extlib/benz/include/picrin/gc.h b/extlib/benz/include/picrin/gc.h
index 9f165d80..c7ed0426 100644
--- a/extlib/benz/include/picrin/gc.h
+++ b/extlib/benz/include/picrin/gc.h
@@ -14,8 +14,8 @@ extern "C" {
 
 struct pic_heap;
 
-struct pic_heap *pic_heap_open();
-void pic_heap_close(struct pic_heap *);
+struct pic_heap *pic_heap_open(pic_state *);
+void pic_heap_close(pic_state *, struct pic_heap *);
 
 #if defined(__cplusplus)
 }
diff --git a/extlib/benz/state.c b/extlib/benz/state.c
index 51f8189e..cc2042f6 100644
--- a/extlib/benz/state.c
+++ b/extlib/benz/state.c
@@ -49,7 +49,7 @@ pic_open(int argc, char *argv[], char **envp)
   pic->xpend = pic->xpbase + PIC_RESCUE_SIZE;
 
   /* memory heap */
-  pic->heap = pic_heap_open();
+  pic->heap = pic_heap_open(pic);
 
   /* symbol table */
   xh_init_str(&pic->syms, sizeof(pic_sym *));
@@ -232,7 +232,7 @@ pic_close(pic_state *pic)
   pic_gc_run(pic);
 
   /* free heaps */
-  pic_heap_close(pic->heap);
+  pic_heap_close(pic, pic->heap);
 
   /* free runtime context */
   free(pic->stbase);