diff --git a/README.md b/README.md
index c6047f5..99be61c 100644
--- a/README.md
+++ b/README.md
@@ -12,6 +12,8 @@ gem "singed"
 
 Then run `bundle install`
 
+Then run `npm install -g speedscope`
+
 ## Usage
 
 Simplest is calling with a block: