diff --git a/app/assets/javascripts/discourse/lib/url.js.es6 b/app/assets/javascripts/discourse/lib/url.js.es6
index 7f2d1bc6c44..ddc964cbad9 100644
--- a/app/assets/javascripts/discourse/lib/url.js.es6
+++ b/app/assets/javascripts/discourse/lib/url.js.es6
@@ -272,7 +272,7 @@ const DiscourseURL = Ember.Object.createWithMixins({
 
   // This has been extracted so it can be tested.
   origin: function() {
-    return window.location.origin;
+    return window.location.origin + (Discourse.BaseUri === "/" ? '' : Discourse.BaseUri);
   },
 
   /**
diff --git a/test/javascripts/lib/url-test.js.es6 b/test/javascripts/lib/url-test.js.es6
index 0598c32e543..39941fd00e5 100644
--- a/test/javascripts/lib/url-test.js.es6
+++ b/test/javascripts/lib/url-test.js.es6
@@ -16,3 +16,10 @@ test("isInternal with a HTTPS url", function() {
   sandbox.stub(DiscourseURL, "origin").returns("https://eviltrout.com");
   ok(DiscourseURL.isInternal("http://eviltrout.com/monocle"), "HTTPS urls match HTTP urls");
 });
+
+test("isInternal on subfolder install", function() {
+  sandbox.stub(DiscourseURL, "origin").returns("http://eviltrout.com/forum");
+  not(DiscourseURL.isInternal("http://eviltrout.com"), "the host root is not internal");
+  not(DiscourseURL.isInternal("http://eviltrout.com/tophat"), "a url on the same host but on a different folder is not internal");
+  ok(DiscourseURL.isInternal("http://eviltrout.com/forum/moustache"), "a url on the same host and on the same folder is internal");
+});