diff --git a/class.c b/class.c
index d73724bd60..f0b6ba0c07 100644
--- a/class.c
+++ b/class.c
@@ -1773,16 +1773,6 @@ rb_define_attr(VALUE klass, const char *name, int read, int write)
     rb_attr(klass, rb_intern(name), read, write, FALSE);
 }
 
-int
-rb_obj_basic_to_s_p(VALUE obj)
-{
-    const rb_method_entry_t *me = rb_method_entry(CLASS_OF(obj), rb_intern("to_s"));
-    if (me && me->def && me->def->type == VM_METHOD_TYPE_CFUNC &&
-	me->def->body.cfunc.func == rb_any_to_s)
-	return 1;
-    return 0;
-}
-
 VALUE
 rb_keyword_error_new(const char *error, VALUE keys)
 {
diff --git a/internal.h b/internal.h
index a474830a2e..81f4d2b91d 100644
--- a/internal.h
+++ b/internal.h
@@ -1055,7 +1055,6 @@ VALUE rb_obj_methods(int argc, const VALUE *argv, VALUE obj);
 VALUE rb_obj_protected_methods(int argc, const VALUE *argv, VALUE obj);
 VALUE rb_obj_private_methods(int argc, const VALUE *argv, VALUE obj);
 VALUE rb_obj_public_methods(int argc, const VALUE *argv, VALUE obj);
-int rb_obj_basic_to_s_p(VALUE);
 VALUE rb_special_singleton_class(VALUE);
 VALUE rb_singleton_class_clone_and_attach(VALUE obj, VALUE attach);
 VALUE rb_singleton_class_get(VALUE obj);