diff --git a/app/assets/javascripts/discourse.js b/app/assets/javascripts/discourse.js
index 96f4c90c6..5b16593a8 100644
--- a/app/assets/javascripts/discourse.js
+++ b/app/assets/javascripts/discourse.js
@@ -16,13 +16,10 @@ window.Discourse = Ember.Application.createWithMixins(Discourse.Ajax, {
     // if it's a non relative URL, return it.
     if (url !== '/' && !/^\/[^\/]/.test(url)) return url;
 
-    var u = Discourse.BaseUri === undefined ? "/" : Discourse.BaseUri;
+    if (url.indexOf(Discourse.BaseUri) !== -1) return url;
+    if (url[0] !== "/") url = "/" + url;
 
-    if (u[u.length-1] === '/') u = u.substring(0, u.length-1);
-    if (url.indexOf(u) !== -1) return url;
-    if (u.length > 0  && url[0] !== "/") url = "/" + url;
-
-    return u + url;
+    return Discourse.BaseUri + url;
   },
 
   getURLWithCDN: function(url) {
diff --git a/app/assets/javascripts/discourse/lib/discourse-location.js.es6 b/app/assets/javascripts/discourse/lib/discourse-location.js.es6
index b7299f2c0..a126bf783 100644
--- a/app/assets/javascripts/discourse/lib/discourse-location.js.es6
+++ b/app/assets/javascripts/discourse/lib/discourse-location.js.es6
@@ -62,11 +62,9 @@ const DiscourseLocation = Ember.Object.extend({
   */
   getURL() {
     const location = get(this, 'location');
-    let rootURL = (Discourse.BaseUri === undefined ? "/" : Discourse.BaseUri);
     let url = location.pathname;
 
-    rootURL = rootURL.replace(/\/$/, '');
-    url = url.replace(rootURL, '');
+    url = url.replace(Discourse.BaseUri, '');
 
     const search = location.search || '';
     url += search;
diff --git a/app/assets/javascripts/discourse/router.js.es6 b/app/assets/javascripts/discourse/router.js.es6
index fc2a6f879..950e78cb8 100644
--- a/app/assets/javascripts/discourse/router.js.es6
+++ b/app/assets/javascripts/discourse/router.js.es6
@@ -1,4 +1,4 @@
-const rootURL = Discourse.BaseUri && Discourse.BaseUri !== "/" ? Discourse.BaseUri : undefined;
+const rootURL = Discourse.BaseUri;
 
 const BareRouter = Ember.Router.extend({
   rootURL,
diff --git a/app/models/admin_dashboard_data.rb b/app/models/admin_dashboard_data.rb
index 33e34d9ff..5cfa8bea2 100644
--- a/app/models/admin_dashboard_data.rb
+++ b/app/models/admin_dashboard_data.rb
@@ -62,7 +62,7 @@ class AdminDashboardData
                       :failing_emails_check, :default_logo_check, :contact_email_check,
                       :send_consumer_email_check, :title_check,
                       :site_description_check, :site_contact_username_check,
-                      :notification_email_check
+                      :notification_email_check, :subfolder_ends_in_slash_check
 
     add_problem_check do
       sidekiq_check || queue_size_check
@@ -201,4 +201,8 @@ class AdminDashboardData
     I18n.t('dashboard.ruby_version_warning') if RUBY_VERSION == '2.0.0' and RUBY_PATCHLEVEL < 247
   end
 
+  def subfolder_ends_in_slash_check
+    I18n.t('dashboard.subfolder_ends_in_slash') if Discourse.base_uri =~ /\/$/
+  end
+
 end
diff --git a/app/views/common/_discourse_javascript.html.erb b/app/views/common/_discourse_javascript.html.erb
index 60bd01460..813581924 100644
--- a/app/views/common/_discourse_javascript.html.erb
+++ b/app/views/common/_discourse_javascript.html.erb
@@ -35,7 +35,7 @@
 <script>
   Discourse.CDN = '<%= Rails.configuration.action_controller.asset_host %>';
   Discourse.BaseUrl = '<%= RailsMultisite::ConnectionManagement.current_hostname %>'.replace(/:[\d]*$/,"");
-  Discourse.BaseUri = '<%= Discourse::base_uri "/" %>';
+  Discourse.BaseUri = '<%= Discourse::base_uri %>';
   Discourse.Environment = '<%= Rails.env %>';
   Discourse.SiteSettings = PreloadStore.get('siteSettings');
   Discourse.LetterAvatarVersion = '<%= LetterAvatar.version %>';
diff --git a/config/locales/server.en.yml b/config/locales/server.en.yml
index 8ee1d22c4..b9a1cc10b 100644
--- a/config/locales/server.en.yml
+++ b/config/locales/server.en.yml
@@ -744,6 +744,7 @@ en:
     consumer_email_warning: "Your site is configured to use Gmail (or another consumer email service) to send email. <a href='http://support.google.com/a/bin/answer.py?hl=en&answer=166852' target='_blank'>Gmail limits how many emails you can send</a>. Consider using an email service provider like mandrill.com to ensure email deliverability."
     site_contact_username_warning: "Enter the name of a friendly staff user account to send important automated messages from. Update site_contact_username in <a href='/admin/site_settings'>Site Settings</a>."
     notification_email_warning: "Notification emails are not being sent from a valid email address on your domain; email delivery will be erratic and unreliable. Please set notification_email to a valid local email address in <a href='/admin/site_settings'>Site Settings</a>."
+    subfolder_ends_in_slash: "Your subfolder setup is incorrect; the DISCOURSE_RELATIVE_URL_ROOT ends in a slash."
 
   content_types:
     education_new_reply:
diff --git a/lib/pretty_text.rb b/lib/pretty_text.rb
index e0096008a..f3acfbc09 100644
--- a/lib/pretty_text.rb
+++ b/lib/pretty_text.rb
@@ -141,7 +141,7 @@ module PrettyText
   def self.decorate_context(context)
     context.eval("Discourse.CDN = '#{Rails.configuration.action_controller.asset_host}';")
     context.eval("Discourse.BaseUrl = '#{RailsMultisite::ConnectionManagement.current_hostname}'.replace(/:[\d]*$/,'');")
-    context.eval("Discourse.BaseUri = '#{Discourse::base_uri("/")}';")
+    context.eval("Discourse.BaseUri = '#{Discourse::base_uri}';")
     context.eval("Discourse.SiteSettings = #{SiteSetting.client_settings_json};")
 
     context.eval("Discourse.getURL = function(url) {
diff --git a/test/javascripts/lib/computed-test.js.es6 b/test/javascripts/lib/computed-test.js.es6
index 4a228d33b..a708ac21e 100644
--- a/test/javascripts/lib/computed-test.js.es6
+++ b/test/javascripts/lib/computed-test.js.es6
@@ -98,7 +98,7 @@ test("url", function() {
   t = testClass.create({ username: 'eviltrout' });
   equal(t.get('userUrl'), "/users/eviltrout", "it supports urls without a prefix");
 
-  Discourse.BaseUri = "/prefixed/";
+  Discourse.BaseUri = "/prefixed";
   t = testClass.create({ username: 'eviltrout' });
   equal(t.get('userUrl'), "/prefixed/users/eviltrout", "it supports urls with a prefix");
 });
diff --git a/test/javascripts/test_helper.js b/test/javascripts/test_helper.js
index f75d5d897..4e0e1c51b 100644
--- a/test/javascripts/test_helper.js
+++ b/test/javascripts/test_helper.js
@@ -88,7 +88,7 @@ QUnit.testStart(function(ctx) {
 
   // Allow our tests to change site settings and have them reset before the next test
   Discourse.SiteSettings = dup(Discourse.SiteSettingsOriginal);
-  Discourse.BaseUri = "/";
+  Discourse.BaseUri = "";
   Discourse.BaseUrl = "localhost";
   Discourse.Session.resetCurrent();
   Discourse.User.resetCurrent();