diff --git a/app/helpers/application_helper.rb b/app/helpers/application_helper.rb
index 86848fb5..5709cca2 100644
--- a/app/helpers/application_helper.rb
+++ b/app/helpers/application_helper.rb
@@ -170,7 +170,8 @@ module ApplicationHelper
       elsif options[:full]
         "#{user.nick} (#{user.first_name} #{user.last_name})"
       else
-        user.nick
+        # when use_nick was changed from false to true, users may exist without nick
+        user.nick.nil? ? I18n.t('helpers.application.nick_fallback') : user.nick
       end
     else
       "#{user.first_name} #{user.last_name}" + (options[:unique] ? " (\##{user.id})" : '')
diff --git a/app/models/user.rb b/app/models/user.rb
index 5bbb6b8d..7335f925 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -161,8 +161,12 @@ class User < ActiveRecord::Base
   # XXX this is view-related; need to move out things like token_attributes
   #     then this can be removed
   def display
-    # would be sensible to match ApplicationController#show_user
-    FoodsoftConfig[:use_nick] ? nick : name
+    # would be sensible to match ApplicationHelper#show_user
+    if FoodsoftConfig[:use_nick]
+      nick.nil? ? I18n.t('helpers.application.nick_fallback') : nick
+    else
+      name
+    end
   end
 
   def token_attributes
diff --git a/app/views/admin/base/index.html.haml b/app/views/admin/base/index.html.haml
index 01cc5aaa..ed13be09 100644
--- a/app/views/admin/base/index.html.haml
+++ b/app/views/admin/base/index.html.haml
@@ -15,7 +15,7 @@
             %th= t '.created_at'
         - for user in @users
           %tr{:class => cycle('even','odd', :name => 'users')}
-            %td= link_to show_user(user, full: true), [:admin, user]
+            %td= link_to show_user(user), [:admin, user]
             - if FoodsoftConfig[:use_nick]
               %td= link_to user.name
             %td= format_date(user.created_on)
diff --git a/app/views/admin/users/_users.html.haml b/app/views/admin/users/_users.html.haml
index 2f085f7b..5fd16bf5 100644
--- a/app/views/admin/users/_users.html.haml
+++ b/app/views/admin/users/_users.html.haml
@@ -14,7 +14,7 @@
   %tbody
     - for user in @users 
       %tr
-        %td= link_to show_user(user, full: true), [:admin, user]
+        %td= link_to show_user(user), [:admin, user]
         - if FoodsoftConfig[:use_nick]
           %td= user.name
         %td= user.email
diff --git a/app/views/foodcoop/users/_users.html.haml b/app/views/foodcoop/users/_users.html.haml
index 2a464c67..b3d27b78 100644
--- a/app/views/foodcoop/users/_users.html.haml
+++ b/app/views/foodcoop/users/_users.html.haml
@@ -15,7 +15,7 @@
     - for user in @users
       %tr
         - if FoodsoftConfig[:use_nick]
-          %td= user.nick
+          %td= show_user user
         %td= user.name  if @current_user.role_admin? || user.settings.profile["name_is_public"] || !FoodsoftConfig[:use_nick]
         %td= user.email if @current_user.role_admin? || user.settings.profile["email_is_public"]
         %td= user.phone if @current_user.role_admin? || user.settings.profile["phone_is_public"]
diff --git a/config/locales/en.yml b/config/locales/en.yml
index d21665ec..4d334b7c 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -864,6 +864,7 @@ en:
   helpers:
     application:
       edit_user: Edit user
+      nick_fallback: (empty username)
       role_admin: Admin
       role_article_meta: Articles
       role_finance: Finance