diff --git a/lib/jekyll/site.rb b/lib/jekyll/site.rb
index aadfb8d0..96910255 100644
--- a/lib/jekyll/site.rb
+++ b/lib/jekyll/site.rb
@@ -528,7 +528,7 @@ module Jekyll
     end
 
     def sanitize_filename(name)
-      name.gsub!(/[^\w\s_-]+/, '')
+      name.gsub!(/[^\w\s-]+/, '')
       name.gsub!(/(^|\b\s)\s+($|\s?\b)/, '\\1\\2')
       name.gsub(/\s+/, '_')
     end