diff --git a/seahub/api2/endpoints/file_tag.py b/seahub/api2/endpoints/file_tag.py
index 2aa5487f52..9e125e6fd5 100644
--- a/seahub/api2/endpoints/file_tag.py
+++ b/seahub/api2/endpoints/file_tag.py
@@ -121,7 +121,7 @@ class FileTagsView(APIView):
             name_list = [name.strip() for name in names.split(",")]
             for name in name_list:
                 if not check_tagname(name):
-                    error_msg = _(u'Tag can only contain letters, numbers, dot, hyphen or underscore')
+                    error_msg = _(u'Tag can only contain letters, numbers, dot, hyphen or underscore.')
                     return api_error(status.HTTP_400_BAD_REQUEST, error_msg)
 
         FileTag.objects.delete_all_filetag_by_path(repo_id, parent_path,
@@ -145,7 +145,7 @@ class FileTagsView(APIView):
         name_list = [name.strip() for name in names.split(",")]
         for name in name_list:
             if not check_tagname(name):
-                error_msg = _(u'Tag can only contain letters, numbers, dot, hyphen or underscore')
+                error_msg = _(u'Tag can only contain letters, numbers, dot, hyphen or underscore.')
                 return api_error(status.HTTP_400_BAD_REQUEST, error_msg)
 
         res_tag_list = []
@@ -165,7 +165,7 @@ class FileTagView(APIView):
     @check_parameter
     def delete(self, request, repo_id, parent_path, filename, name, is_dir):
         if not name or not check_tagname(name):
-            error_msg = _(u'Tag can only contain letters, numbers, dot, hyphen or underscore')
+            error_msg = _(u'Tag can only contain letters, numbers, dot, hyphen or underscore.')
             return api_error(status.HTTP_400_BAD_REQUEST, error_msg)
         if FileTag.objects.delete_file_tag_by_path(repo_id,
                 parent_path,filename,is_dir,name):
diff --git a/seahub/api2/endpoints/revision_tag.py b/seahub/api2/endpoints/revision_tag.py
index 68924d3457..a8a92a92f8 100644
--- a/seahub/api2/endpoints/revision_tag.py
+++ b/seahub/api2/endpoints/revision_tag.py
@@ -12,7 +12,7 @@ from django.utils.translation import ugettext as _
 from seahub.api2.throttling import UserRateThrottle
 from seahub.api2.authentication import TokenAuthentication
 from seahub.api2.utils import api_error
-from seahub.revision_tag.models import Tags, RevisionTags
+from seahub.revision_tag.models import RevisionTags
 from seahub.views import check_folder_permission
 
 import seaserv
@@ -52,7 +52,7 @@ def check_parameter(func):
             names = [name.strip() for name in tag_names.split(',')]
             for name in names:
                 if not check_tagname(name):
-                    error_msg = _("Tag can only contains letters, numbers, dot, hyphen or underscore")
+                    error_msg = _("Tag can only contain letters, numbers, dot, hyphen or underscore.")
                     return api_error(status.HTTP_400_BAD_REQUEST, error_msg)
 
         if check_folder_permission(request, repo_id, '/') != 'rw':