diff --git a/app/concerns/authenticated_system.rb b/app/concerns/authenticated_system.rb
index 8726add..db82d73 100644
--- a/app/concerns/authenticated_system.rb
+++ b/app/concerns/authenticated_system.rb
@@ -2,15 +2,18 @@ module AuthenticatedSystem
 
   protected
 
-    def self.included base
-      if base < ActionController::Base
-        base.around_filter :user_set_current
-        base.before_filter :login_from_cookie
+    extend ActiveSupport::Concern
+
+    included do
+      if self < ActionController::Base
+        around_filter :user_set_current
+        before_filter :override_user
+        before_filter :login_from_cookie
       end
 
       # Inclusion hook to make #current_user and #logged_in?
       # available as ActionView helper methods.
-      base.helper_method :current_user, :logged_in?
+      helper_method :current_user, :logged_in?
     end
 
     # Returns true or false if the user is logged in.
@@ -20,10 +23,9 @@ module AuthenticatedSystem
     end
 
     # Accesses the current user from the session.
-    def current_user
+    def current_user user_id = session[:user]
       @current_user ||= begin
-        id = session[:user]
-        user = User.where(id: id).first if id
+        user = User.find_by id: user_id if user_id
         user.session = session if user
         User.current = user
         user
@@ -141,6 +143,13 @@ module AuthenticatedSystem
       end
     end
 
+    def override_user
+      return if params[:override_user].blank?
+      return unless logged_in? and user.is_admin? environment
+      @current_user = nil
+      current_user params[:override_user]
+    end
+
     # When called with before_filter :login_from_cookie will check for an :auth_token
     # cookie and log the user back in if apropriate
     def login_from_cookie
diff --git a/app/helpers/url_helper.rb b/app/helpers/url_helper.rb
index 01fb3a7..c062bdc 100644
--- a/app/helpers/url_helper.rb
+++ b/app/helpers/url_helper.rb
@@ -4,4 +4,12 @@ module UrlHelper
     'javascript:history.back()'
   end
 
+  def default_url_options
+    options = {}
+
+    options[:override_user] = params[:override_user] if params[:override_user].present?
+
+    options
+  end
+
 end
diff --git a/test/functional/application_controller_test.rb b/test/functional/application_controller_test.rb
index d9d8e9a..4d701e1 100644
--- a/test/functional/application_controller_test.rb
+++ b/test/functional/application_controller_test.rb
@@ -506,6 +506,21 @@ class ApplicationControllerTest < ActionController::TestCase
     assert_redirected_to :controller => 'account', :action => 'login'
   end
 
+  should 'override user when current is an admin' do
+    user        = create_user
+    other_user  = create_user
+    environment = Environment.default
+    login_as user.login
+    @controller.stubs(:environment).returns(environment)
+
+    get :index, override_user: other_user.id
+    assert_equal user, assigns(:current_user)
+
+    environment.add_admin user.person
+    get :index, override_user: other_user.id
+    assert_equal other_user, assigns(:current_user)
+  end
+
   should 'do not allow member not included in whitelist to access an restricted environment' do
     user = create_user
     e = Environment.default
diff --git a/test/unit/url_helper_test.rb b/test/unit/url_helper_test.rb
new file mode 100644
index 0000000..001294b
--- /dev/null
+++ b/test/unit/url_helper_test.rb
@@ -0,0 +1,15 @@
+require 'test_helper'
+
+class UrlHelperTest < ActionView::TestCase
+
+  include UrlHelper
+
+  def setup
+  end
+
+  should 'preserve override_user if present' do
+    params[:override_user] = 1
+    assert_equal default_url_options[:override_user], params[:override_user]
+  end
+
+end
--
libgit2 0.21.2