diff --git a/static/js/ui.js b/static/js/ui.js
index 67dc340809..34b48d35a6 100644
--- a/static/js/ui.js
+++ b/static/js/ui.js
@@ -419,8 +419,11 @@ function left_userlist_get_new_heights() {
     var invite_user_link_height = $("#invite-user-link").outerHeight(true) || 0;
     var share_the_love_height = $("#share-the-love").is(":visible") ? $("#share-the-love").outerHeight(true) : 0;
 
-    var stream_filters_real_height = $("#stream_filters").prop("scrollHeight");
-    var user_list_real_height = $("#user_presences").prop("scrollHeight");
+    var stream_filters = $('#stream_filters').expectOne();
+    var user_presences = $('#user_presences').expectOne();
+
+    var stream_filters_real_height = stream_filters.prop("scrollHeight");
+    var user_list_real_height = user_presences.prop("scrollHeight");
 
     res.bottom_whitespace_height = viewport_height * 0.4;
 
@@ -435,9 +438,9 @@ function left_userlist_get_new_heights() {
                                 - $("#global_filters").outerHeight(true)
                                 - $("#streams_header").outerHeight(true)
                                 - $("#userlist-header").outerHeight(true)
-                                - parseInt($("#stream_filters").css("marginBottom"),10)
-                                - parseInt($("#user_presences").css("marginTop"), 10)
-                                - parseInt($("#user_presences").css("marginBottom"), 10)
+                                - parseInt(stream_filters.css("marginBottom"),10)
+                                - parseInt(user_presences.css("marginTop"), 10)
+                                - parseInt(user_presences.css("marginBottom"), 10)
                                 - invite_user_link_height
                                 - share_the_love_height
                                 - 15;