diff --git a/app/assets/javascripts/vue-shared.js b/app/assets/javascripts/vue-shared.js
index d57ad4f9b..4c8a28979 100644
--- a/app/assets/javascripts/vue-shared.js
+++ b/app/assets/javascripts/vue-shared.js
@@ -10,7 +10,7 @@ Vue.use(VueResource);
 Vue.use(EventBus);
 Vue.use(Alert);
 
-Vue.http.options.root = window.API_ROOT_URL;
+Vue.http.options.root = window.API_URL;
 
 Vue.http.interceptors.push((_request, next) => {
   window.$.active = window.$.active || 0;
diff --git a/app/helpers/application_helper.rb b/app/helpers/application_helper.rb
index acefb9bcb..a12f791ac 100644
--- a/app/helpers/application_helper.rb
+++ b/app/helpers/application_helper.rb
@@ -12,6 +12,14 @@ def app_host
     request.env["HTTP_HOST"]
   end
 
+  def app_relative_url_root
+    ENV["RAILS_RELATIVE_URL_ROOT"] || ""
+  end
+
+  def app_path
+    File.join(app_host, app_relative_url_root)
+  end
+
   def js_route
     action_name = ACTION_ALIASES[controller.action_name] || controller.action_name
 
diff --git a/app/views/layouts/application.html.slim b/app/views/layouts/application.html.slim
index 250bd90bb..fc01a5833 100644
--- a/app/views/layouts/application.html.slim
+++ b/app/views/layouts/application.html.slim
@@ -29,7 +29,7 @@ html
     meta content="#205683" name="theme-color"
 
     javascript:
-      window.API_ROOT_URL = '//#{app_host}';
+      window.API_URL = '//#{app_path}';
     = javascript_include_tag(*webpack_asset_paths("application"))
     = yield :js_header