From c8f0e8f272c51674453c827024ae4356f4979595 Mon Sep 17 00:00:00 2001
From: Wen Kokke <wenkokke@users.noreply.github.com>
Date: Tue, 16 Oct 2018 16:18:51 +0100
Subject: [PATCH] Added clause about gnu-sed

---
 README.md | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/README.md b/README.md
index c29db46b..ef3120ce 100644
--- a/README.md
+++ b/README.md
@@ -57,6 +57,17 @@ unzip, and from within the directory run
     bundle install
     bundle exec jekyll serve
 
+### GNU sed and macOS
+
+The version of sed that ships with macOS is not fully compatible with the GNU sed.
+Therefore, you may get errors such as:
+```
+sed: 1: "out/plfa/Bisimulation.md": invalid command code o
+```
+You can fix this error by installing a GNU compatible version of sed, e.g. using [Homebrew](https://brew.sh/):
+```
+brew install gnu-sed --with-default-names
+```
 
 ## Updates to agda2html