diff --git a/requirements.txt b/requirements.txt
index a136e24..6c6643f 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -4,6 +4,7 @@ bcrypt
 # For running the etiquette webserver.
 flask
 gevent
+gunicorn
 
 # For probing and thumbnailing image files.
 pillow
@@ -17,5 +18,8 @@ send2trash
 # For serving downloadable zip files as a generator.
 zipstream
 
+# For serving Atom feeds
+bs4
+
 # My own variety toolkit.
 voussoirkit