diff --git a/README.mkd b/README.mkd
index 940c8a2..32a22bf 100644
--- a/README.mkd
+++ b/README.mkd
@@ -310,6 +310,7 @@ Here are some things you can check:
 * Your Vim supports signs (`:echo has('signs')` should give `1`).
 * Your file is being tracked by git and has unstaged, saved changes.
 * If you use the Fish shell, or another non-POSIX shell, add `set shell=/bin/bash` to your `~/.vimrc`.
+* Make sure your grep produces colourless output, e.g. with `export GREP_OPTIONS='--color=auto'`.
 
 
 ### Shameless Plug