diff --git a/zephyr/static/js/notifications_bar.js b/zephyr/static/js/notifications_bar.js
index 931f77fe1d..fc26522e0d 100644
--- a/zephyr/static/js/notifications_bar.js
+++ b/zephyr/static/js/notifications_bar.js
@@ -29,8 +29,10 @@ function hide() {
 // If there's a custom message, or if the last message is off the bottom of the
 // screen, then show the notifications bar.
 exports.update = function (num_unread) {
-    if (rows.last_visible().offset() !== null // otherwise the next line will error
-        && rows.last_visible().offset().top + rows.last_visible().height() > viewport.scrollTop() + viewport.height() - $("#compose").height()
+    var last_row = rows.last_visible();
+    if (last_row
+        && last_row.offset() !== null // otherwise the next line will error
+        && viewport.is_below_visible_bottom(last_row.offset().top + last_row.height())
         && num_unread > 0)
         show();
     else
diff --git a/zephyr/static/js/viewport.js b/zephyr/static/js/viewport.js
index f7a4353a06..6a73b83e5d 100644
--- a/zephyr/static/js/viewport.js
+++ b/zephyr/static/js/viewport.js
@@ -49,6 +49,10 @@ exports.at_bottom = function () {
     return bottom + 2 >= window_size;
 };
 
+exports.is_below_visible_bottom = function (offset) {
+    return offset > viewport.scrollTop() + viewport.height() - $("#compose").height();
+};
+
 exports.set_message_position = function (message_top, message_height, viewport_info, ratio) {
     // message_top = offset of the top of a message that you are positioning
     // message_height = height of the message that you are positioning