diff --git a/autoload/zencoding/lang/haml.vim b/autoload/zencoding/lang/haml.vim
index be421c1..be8de24 100644
--- a/autoload/zencoding/lang/haml.vim
+++ b/autoload/zencoding/lang/haml.vim
@@ -26,7 +26,7 @@ function! zencoding#lang#haml#toString(settings, current, type, inline, filters,
   if len(current.name) > 0
     let str .= '%' . current_name
     let tmp = ''
-    for attr in current.attrs_order
+    for attr in zencoding#util#unique(current.attrs_order)
       if !has_key(current.attr, attr)
         continue
       endif
diff --git a/autoload/zencoding/lang/html.vim b/autoload/zencoding/lang/html.vim
index d7a1e63..12980cc 100644
--- a/autoload/zencoding/lang/html.vim
+++ b/autoload/zencoding/lang/html.vim
@@ -322,7 +322,7 @@ function! zencoding#lang#html#toString(settings, current, type, inline, filters,
   endif
   if len(current_name) > 0
   let str .= '<' . current_name
-  for attr in current.attrs_order
+  for attr in zencoding#util#unique(current.attrs_order)
     if !has_key(current.attr, attr)
       continue
     endif
diff --git a/autoload/zencoding/lang/slim.vim b/autoload/zencoding/lang/slim.vim
index 15bc968..16597c4 100644
--- a/autoload/zencoding/lang/slim.vim
+++ b/autoload/zencoding/lang/slim.vim
@@ -25,7 +25,7 @@ function! zencoding#lang#slim#toString(settings, current, type, inline, filters,
   endif
   if len(current.name) > 0
     let str .= current_name
-    for attr in current.attrs_order
+    for attr in zencoding#util#unique(current.attrs_order)
       if !has_key(current.attr, attr)
         continue
       endif
diff --git a/autoload/zencoding/util.vim b/autoload/zencoding/util.vim
index 5a028c9..ebc3a4b 100644
--- a/autoload/zencoding/util.vim
+++ b/autoload/zencoding/util.vim
@@ -247,3 +247,15 @@ function! zencoding#util#isImageMagickInstalled()
   endif
   return executable('identify')
 endfunction
+
+function! zencoding#util#unique(arr)
+  let m = {}
+  let r = []
+  for i in a:arr
+    if !has_key(m, i)
+      let m[i] = 1
+      call add(r, i)
+    endif
+  endfor
+  return r
+endfunction