diff --git a/testing/mochitest/README.txt b/testing/mochitest/README.txt
index 102f55fe9ed2..1de095fc1f7d 100644
--- a/testing/mochitest/README.txt
+++ b/testing/mochitest/README.txt
@@ -4,7 +4,8 @@
 
 Steps to get started:
 
- 1.) Right now, you will need to edit some constants in runtests.pl.
+ 1.) Right now, you will need to edit some constants in runtests.pl. Windows
+     is not yet supported.
 
  2.) Start the python server in a separate console: