diff --git a/ChangeLog b/ChangeLog
index c615ded0ac..4e0384458b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Fri Jul 29 10:51:34 2016  Koichi Sasada  <ko1@atdot.net>
+
+	* proc.c (env_write): remove unused function.
+
 Fri Jul 29 10:49:52 2016  Koichi Sasada  <ko1@atdot.net>
 
 	* vm_core.h (VM_LOCAL_P): should return an integer value.
diff --git a/proc.c b/proc.c
index 6c24bbb3e1..15351eb2c5 100644
--- a/proc.c
+++ b/proc.c
@@ -2700,16 +2700,6 @@ localjump_reason(VALUE exc)
 
 rb_cref_t *rb_vm_cref_new_toplevel(void); /* vm.c */
 
-static inline void
-env_write(VALUE envval, const VALUE *ep, int index, VALUE v)
-{
-    VM_ASSERT(VM_ENV_ESCAPED_P(ep));
-    VM_ASSERT(envval == VM_ENV_ENVVAL(ep));
-    VM_ASSERT(vm_assert_env(envval));
-
-    RB_OBJ_WRITE(envval, &ep[index], v);
-}
-
 static const rb_env_t *
 env_clone(const rb_env_t *env, const rb_cref_t *cref)
 {