diff --git a/altair/examples/pyramid.py b/altair/examples/pyramid.py
index a53b90e05..676d77e88 100644
--- a/altair/examples/pyramid.py
+++ b/altair/examples/pyramid.py
@@ -3,6 +3,7 @@
 -----------------
 Altair reproduction of http://robslink.com/SAS/democd91/pyramid_pie.htm
 """
+# category: case studies
 import altair as alt
 import pandas as pd
 
@@ -16,4 +17,4 @@
         scale=alt.Scale(domain=category, range=color),
         legend=alt.Legend(title=None, orient='none', legendX=160, legendY=50)),
     order='value:Q'
-).properties(width=150, height=150).configure_view(strokeOpacity=0)
\ No newline at end of file
+).properties(width=150, height=150).configure_view(strokeOpacity=0)