diff --git a/models/site.rb b/models/site.rb
index b7a15fa8..0d01dd4f 100644
--- a/models/site.rb
+++ b/models/site.rb
@@ -39,7 +39,7 @@ class Site < Sequel::Model
   }
 
   VALID_EXTENSIONS = %w{
-    html htm txt text css js jpg jpeg png gif svg md markdown eot ttf woff woff2 json geojson csv tsv mf ico pdf asc key pgp xml mid midi manifest otf webapp less sass rss kml dae obj mtl scss webp xcf epub gltf bin webmanifest
+    html htm txt text css js jpg jpeg png gif svg md markdown eot ttf woff woff2 json geojson csv tsv mf ico pdf asc key pgp xml mid midi manifest otf webapp less sass rss kml dae obj mtl scss webp xcf epub gltf bin webmanifest knowl
   }
 
   VALID_EDITABLE_EXTENSIONS = %w{