diff --git a/include/picrin.h b/include/picrin.h
index 91ca2921..955dac01 100644
--- a/include/picrin.h
+++ b/include/picrin.h
@@ -11,7 +11,7 @@
 
 struct pic_code;
 
-typedef struct pic_callinfo {
+typedef struct {
   int argc;
   struct pic_code *pc;
   pic_value *fp;
diff --git a/include/picrin/proc.h b/include/picrin/proc.h
index e92ad6c8..d1ca2aab 100644
--- a/include/picrin/proc.h
+++ b/include/picrin/proc.h
@@ -4,7 +4,7 @@
 struct pic_env {
   PIC_OBJECT_HEADER
   pic_value *values;
-  int num_val;
+  int valuec;
   struct pic_env *up;
 };
 
diff --git a/src/gc.c b/src/gc.c
index c717e608..d95dd01f 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -159,7 +159,7 @@ gc_mark_object(pic_state *pic, struct pic_object *obj)
     struct pic_env *env = (struct pic_env *)obj;
     int i;
 
-    for (i = 0; i < env->num_val; ++i) {
+    for (i = 0; i < env->valuec; ++i) {
       gc_mark(pic, env->values[i]);
     }
     if (env->up) {
diff --git a/src/vm.c b/src/vm.c
index c52eb707..2271dd2e 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -370,9 +370,9 @@ pic_apply(pic_state *pic, struct pic_proc *proc, pic_value argv)
 	/* prepare env */
 	ci->env = (struct pic_env *)pic_obj_alloc(pic, sizeof(struct pic_env), PIC_TT_ENV);
 	ci->env->up = proc->env;
-	ci->env->num_val = proc->u.irep->argc + proc->u.irep->localc;
-	ci->env->values = (pic_value *)pic_calloc(pic, ci->env->num_val, sizeof(pic_value));
-	for (i = 0; i < ci->env->num_val; ++i) {
+	ci->env->valuec = proc->u.irep->argc + proc->u.irep->localc;
+	ci->env->values = (pic_value *)pic_calloc(pic, ci->env->valuec, sizeof(pic_value));
+	for (i = 0; i < ci->env->valuec; ++i) {
 	  ci->env->values[i] = ci->fp[i];
 	}