From 561009437f37feb6ca5040d0833d17450f39f85f Mon Sep 17 00:00:00 2001
From: Andrew Kane <acekane1@gmail.com>
Date: Sat, 12 Sep 2015 01:02:39 -0700
Subject: [PATCH] Added note about argument error

---
 README.md | 2 ++
 1 file changed, 2 insertions(+), 0 deletions(-)

diff --git a/README.md b/README.md
index 9180eda..e45e7a1 100644
--- a/README.md
+++ b/README.md
@@ -151,6 +151,8 @@ Limit groupings with the `permit` option.
 User.group_by_period(params[:period], :created_at, permit: %w[day week]).count
 ```
 
+Raises an `ArgumentError` for unpermitted periods.
+
 ## Arrays and Hashes
 
 ```ruby
--
libgit2 0.21.0