diff --git a/include/picrin.h b/include/picrin.h
index 626a52a4..3435ee77 100644
--- a/include/picrin.h
+++ b/include/picrin.h
@@ -18,6 +18,7 @@ typedef struct {
   pic_value *sp;
   pic_value *stbase, *stend;
 
+  pic_value sDEFINE, sCONS, sADD;
   struct pic_env *global_env;
 
   struct heap_page *heap;
diff --git a/src/state.c b/src/state.c
index 5d96b76a..80588d95 100644
--- a/src/state.c
+++ b/src/state.c
@@ -35,6 +35,9 @@ pic_open()
   pic->arena_idx = 0;
 
   pic->global_env = pic_new_empty_env();
+  pic->sDEFINE = pic_intern_cstr(pic, "define");
+  pic->sCONS = pic_intern_cstr(pic, "cons");
+  pic->sADD = pic_intern_cstr(pic, "add");
 
   return pic;
 }
diff --git a/src/vm.c b/src/vm.c
index 851f02f1..255f3efc 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -57,9 +57,9 @@ pic_gen(pic_state *pic, struct pic_irep *irep, pic_value obj, struct pic_env *en
 {
   pic_value sDEFINE, sCONS, sADD;
 
-  sDEFINE = pic_intern_cstr(pic, "define");
-  sCONS = pic_intern_cstr(pic, "cons");
-  sADD = pic_intern_cstr(pic, "add");
+  sDEFINE = pic->sDEFINE;
+  sCONS = pic->sCONS;
+  sADD = pic->sADD;
 
   switch (pic_type(obj)) {
   case PIC_TT_SYMBOL: {