diff --git a/pillar/web/jinja.py b/pillar/web/jinja.py
index 97855d39..a342fe88 100644
--- a/pillar/web/jinja.py
+++ b/pillar/web/jinja.py
@@ -22,6 +22,10 @@ def format_undertitle(s):
     Replaces underscores with spaces, and then applies Jinja2's own title filter.
     """
 
+    # Just keep empty strings and Nones as they are.
+    if not s:
+        return s
+
     return jinja2.filters.do_title(s.replace('_', ' '))