diff --git a/templates/repo_file_get.html b/templates/repo_file_get.html
index fccfa0c915..bbb72c3d57 100644
--- a/templates/repo_file_get.html
+++ b/templates/repo_file_get.html
@@ -150,6 +150,6 @@
       });
       });
 {% endif %}
-{% if filetype != 'Text' and filetype != 'Image' and filetype != 'SVG' and filetype != 'Document' and filetype != 'PDF' %}
+{% if filetype == 'Unkown' %}
         $('#file-view').html('<p>该类型文件无法在线查看。<a href="{{ SITE_ROOT }}repo/{{ repo.id }}/{{ obj_id }}/?file_name={{ file_name }}&op=download">下载</a></p>');
 {% endif %}
diff --git a/templates/view_shared_file.html b/templates/view_shared_file.html
index 30e9c66ebb..33c6d43345 100644
--- a/templates/view_shared_file.html
+++ b/templates/view_shared_file.html
@@ -20,8 +20,7 @@
 {% block extra_script %}
 <script type="text/javascript">
     var url = '{{ SITE_ROOT }}repo/{{ repo.id }}/file/get/?t={{ access_token }}&p={{ path|urlencode }}&u={{ username }}',
-        filetype = '{{ filetype }}';
-        
+    
     {% include "repo_file_get.html" %}
 </script>
 {% endblock %}
diff --git a/utils.py b/utils.py
index c51b57c056..9d3b6e6cf2 100644
--- a/utils.py
+++ b/utils.py
@@ -240,7 +240,7 @@ def valid_previewed_file(filename):
     
     """
     fileExt = os.path.splitext(filename)[1][1:]
-    return FILEEXT_TYPE_MAP.get(fileExt)
+    return FILEEXT_TYPE_MAP.get(fileExt) or 'Unkown'
 
 def get_file_revision_id_size (commit_id, path):
     """Given a commit and a file path in that commit, return the seafile id