diff --git a/lib/jekyll/collection.rb b/lib/jekyll/collection.rb
index 03474582..97371ac6 100644
--- a/lib/jekyll/collection.rb
+++ b/lib/jekyll/collection.rb
@@ -105,7 +105,7 @@ module Jekyll
     #
     # Returns a sanitized version of the label.
     def sanitize_label(label)
-      label.gsub(/[^a-z0-9_\-]/i, '')
+      label.gsub(/[^a-z0-9_\-\.]/i, '')
     end
 
     # Produce a representation of this Collection for use in Liquid.