diff --git a/README.md b/README.md
index a7ece9d..81b91c3 100644
--- a/README.md
+++ b/README.md
@@ -21,3 +21,5 @@ To find your profile folder launch the Thunderbird binary with the -P switch or
 On Linux it is under $HOME/.thunderbird/
 
 Create 'chrome' directory in the profile folder and place `userChrome.css` in there.
+
+Restart Thunderbird for the changes to take effect.