diff --git a/binderhub/app.py b/binderhub/app.py
index 560f54506..dad7e1f26 100644
--- a/binderhub/app.py
+++ b/binderhub/app.py
@@ -188,6 +188,16 @@ def _google_analytics_deprecation(self, change):
config=True,
)
+ extra_css = Unicode(
+ "",
+ help="""
+ Extra bits of CSS that should be loaded in each page.
+
+ Omit the
+ {% endif %}