diff --git a/setup.cfg b/setup.cfg
index 1d3c2f3..5171ef4 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -18,6 +18,7 @@ packages = find:
 include_package_data = True
 install_requires=
     beautifulsoup4
+    cssutils
     cryptography
     defusedxml
     Flask