diff --git a/urls.py b/urls.py
index 01ba5e029e..0656809abf 100644
--- a/urls.py
+++ b/urls.py
@@ -17,7 +17,6 @@ from seahub.views import root, peers, myhome, \
 from seahub.notifications.views import notification_list
 from seahub.share.views import share_admin
 from seahub.group.views import group_list
-from seahub.utils import gen_fileext_type_map
 
 # Uncomment the next two lines to enable the admin:
 #from django.contrib import admin
@@ -110,6 +109,3 @@ if settings.DEBUG:
         (r'^%s/(?P<path>.*)$' % (media_url), 'django.views.static.serve', {'document_root': settings.MEDIA_ROOT}),
     )
 
-# Add file extension and type to dictionary at django startup,
-# this function should be called only once. 
-FILEEXT_TYPE_MAP = gen_fileext_type_map()
diff --git a/utils.py b/utils.py
index b2d2ff30f5..7c7ed2fc55 100644
--- a/utils.py
+++ b/utils.py
@@ -237,7 +237,6 @@ def valid_previewed_file(filename):
     Check whether file can preview on web
     
     """
-    from urls import FILEEXT_TYPE_MAP
     fileExt = os.path.splitext(filename)[1][1:]
     return FILEEXT_TYPE_MAP.get(fileExt)
 
@@ -267,3 +266,4 @@ def gen_fileext_type_map():
             d[fileext] = filetype
 
     return d
+FILEEXT_TYPE_MAP = gen_fileext_type_map()