diff --git a/ftplugin/haml.vim b/ftplugin/haml.vim
index e74530b..bdc91d3 100644
--- a/ftplugin/haml.vim
+++ b/ftplugin/haml.vim
@@ -37,6 +37,8 @@ endif
 runtime! ftplugin/ruby.vim ftplugin/ruby_*.vim ftplugin/ruby/*.vim
 let b:did_ftplugin = 1
 
+let &l:define .= empty(&l:define ? '' : '\|') . '^\s*\%(%\w*\)\=\%(\.[[:alnum:]_-]\+\)*#'
+
 " Combine the new set of values with those previously included.
 if exists("b:undo_ftplugin")
   let s:undo_ftplugin = b:undo_ftplugin . " | " . s:undo_ftplugin
@@ -60,7 +62,7 @@ endif
 
 setlocal comments= commentstring=-#\ %s
 
-let b:undo_ftplugin = "setl cms< com< "
+let b:undo_ftplugin = "setl def< cms< com< "
       \ " | unlet! b:browsefilter b:match_words | " . s:undo_ftplugin
 
 let &cpo = s:save_cpo