diff --git a/include/picrin.h b/include/picrin.h
index 79995f24..ec469abe 100644
--- a/include/picrin.h
+++ b/include/picrin.h
@@ -11,12 +11,6 @@ struct pic_env {
   struct pic_env *parent;
 };
 
-struct pic_proc {
-  union {
-    struct pic_irep *irep;
-  } u;
-};
-
 #define PIC_HEAP_SIZE 1024
 
 typedef struct {
diff --git a/include/picrin/value.h b/include/picrin/value.h
index 3666aec1..b2acba8b 100644
--- a/include/picrin/value.h
+++ b/include/picrin/value.h
@@ -23,7 +23,8 @@ enum pic_tt {
   PIC_TT_UNDEF,
   /* heap */
   PIC_TT_PAIR,
-  PIC_TT_SYMBOL
+  PIC_TT_SYMBOL,
+  PIC_TT_PROC
 };
 
 #define PIC_OBJECT_HEADER			\
@@ -44,8 +45,16 @@ struct pic_symbol {
   char *name;
 };
 
+struct pic_proc {
+  PIC_OBJECT_HEADER
+  union {
+    struct pic_irep *irep;
+  } u;
+};
+
 #define pic_pair_ptr(o) ((struct pic_pair *)o.u.data)
 #define pic_symbol_ptr(o) ((struct pic_symbol *)o.u.data)
+#define pic_proc_ptr(o) ((struct pic_proc *)o.u.data)
 
 enum pic_tt pic_type(pic_value);
 
diff --git a/src/vm.c b/src/vm.c
index 439d9cd8..3d5e8c31 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -161,7 +161,7 @@ pic_codegen(pic_state *pic, pic_value obj, struct pic_env *env)
   struct pic_irep *irep;
   struct pic_code *code;
 
-  proc = (struct pic_proc *)malloc(sizeof(struct pic_proc));
+  proc = (struct pic_proc *)pic_gc_alloc(pic, sizeof(struct pic_proc), PIC_TT_PROC);
 
   proc->u.irep = irep = (struct pic_irep *)malloc(sizeof(struct pic_irep));
   irep->code = code = (struct pic_code *)malloc(sizeof(struct pic_code) * 1024);