diff --git a/nbgrader/server_extensions/formgrader/static/js/manage_assignments.js b/nbgrader/server_extensions/formgrader/static/js/manage_assignments.js
index 4a07a0c45..acf940d81 100644
--- a/nbgrader/server_extensions/formgrader/static/js/manage_assignments.js
+++ b/nbgrader/server_extensions/formgrader/static/js/manage_assignments.js
@@ -103,7 +103,7 @@ var AssignmentUI = Backbone.View.extend({
 
         this.$name.append($("<a/>")
             .text(name)
-            .map(linkTo("directory", url_prefix + "/" + this.model.get("source_path")))
+            .map(linkTo("directory", url_prefix + "/" + this.model.get("source_path"), base_url))
         );
 
         // duedate
@@ -150,7 +150,7 @@ var AssignmentUI = Backbone.View.extend({
         var release_path = this.model.get("release_path");
         if (release_path) {
             this.$preview.append($("<a/>")
-                .map(linkTo("directory", url_prefix + "/" + release_path))
+                .map(linkTo("directory", url_prefix + "/" + release_path, base_url))
                 .append($("<span/>")
                     .addClass("glyphicon glyphicon-search")
                     .attr("aria-hidden", "true")
diff --git a/nbgrader/server_extensions/formgrader/static/js/utils.js b/nbgrader/server_extensions/formgrader/static/js/utils.js
index 05c50aec1..1ec55ffb8 100644
--- a/nbgrader/server_extensions/formgrader/static/js/utils.js
+++ b/nbgrader/server_extensions/formgrader/static/js/utils.js
@@ -88,17 +88,20 @@ var insertDataTable = function (tbl) {
     });
 };
 
-var linkTo = function (type, path) {
+var linkTo = function (type, path, base) {
     /*
      * Connect a link in the appropriate manner for the context.
      * - If we're in the outermost frame, assume notebook and use an href.
      * - If we're in an iframe, assume lab and send a message.
      */
     if (window === window.top) {
+        if (typeof base === "undefined") {
+            base = "";
+        }
         var prefix = {
-            notebook: "/notebooks/",
-            file: "/edit/",
-            directory: "/tree/"
+            notebook: base + "/notebooks/",
+            file: base + "/edit/",
+            directory: base + "/tree/"
         }[type];
 
         return (_, el) => {