diff --git a/browse-slack/README.md b/browse-slack/README.md
index 0cca1719..bcbfc7ec 100644
--- a/browse-slack/README.md
+++ b/browse-slack/README.md
@@ -1,4 +1,4 @@
-To try it out:
+To try it out (on Linux; it's unusably slow on other platforms):
 
 1. Import a Slack archive into the data disk by following the instructions at
    the top of `browse-slack/convert_slack.py`.
@@ -12,5 +12,5 @@ To try it out:
 3. Run the code and data disks:
 
 ```
-qemu-system-i386 -m 2G -hda code.img -hdb path/to/data.img
+qemu-system-i386 -accel kvm -m 2G -hda code.img -hdb path/to/data.img
 ```