diff --git a/specs/README.md b/specs/README.md
index cd6579e..9449b5c 100644
--- a/specs/README.md
+++ b/specs/README.md
@@ -2,7 +2,8 @@
 This is a [bikeshed](https://github.com/tabatkins/bikeshed) file, very similar to Markdown.
 
 
-To compile with a nice CC0 logo and not the awful one by default in Bikeshed `python make.py` and this will generate a file `specs.html`
+To compile with a nice CC0 logo and not the awful one by default in Bikeshed `python make.py` and this will generate a file `specs.html`.
+You must `pip install beautifulsoup4`.
 
 
 To convert it to an HTML file with the ugly CC0 image directly: `curl https://api.csswg.org/bikeshed/ -F file=@specs.bs -F force=1 > specs.html`