diff --git a/zephyr/static/js/compose.js b/zephyr/static/js/compose.js
index 92c889d69e..88f0e8a80e 100644
--- a/zephyr/static/js/compose.js
+++ b/zephyr/static/js/compose.js
@@ -44,22 +44,7 @@ function show(tabname, focus_area) {
         var cover = selected_row.offset().top + selected_row.height()
             - $("#compose").offset().top;
         if (cover > 0) {
-            disable_pointer_movement = true;
-            // We use $('html, body') because you can't animate window.scrollTop
-            // on Chrome (http://bugs.jquery.com/ticket/10419).
-            $('html, body').animate({
-                scrollTop: viewport.scrollTop() + cover + 5
-            }, {
-                complete: function () {
-                    // The complete callback is actually called before the
-                    // scrolling has completed, so we try to let scrolling
-                    // finish before allowing pointer movements again or the
-                    // pointer may still move.
-                    setTimeout(function () {
-                        disable_pointer_movement = false;
-                    }, 50);
-                }
-            });
+            viewport.user_initiated_animate_scroll(cover+5);
         }
     });
     focus_area.focus();
diff --git a/zephyr/static/js/message_list.js b/zephyr/static/js/message_list.js
index 3d4ee26222..c277e56861 100644
--- a/zephyr/static/js/message_list.js
+++ b/zephyr/static/js/message_list.js
@@ -488,11 +488,7 @@ MessageList.prototype = {
         }
 
         // Ok, we are finally ready to actually scroll.
-        suppress_scroll_pointer_update = true; // Gets set to false in the scroll handler.
-        var viewport_offset = viewport.scrollTop();
-        // viewport (which is window) doesn't have a scrollTop, so scroll
-        // the closest concept that does.
-        $("html, body").animate({scrollTop: viewport_offset + scroll_amount});
+        viewport.system_initiated_animate_scroll(scroll_amount);
     },
 
     clear_trailing_bookend: function MessageList_clear_trailing_bookend() {
@@ -601,8 +597,7 @@ MessageList.prototype = {
 };
 
 $(document).on('message_selected.zephyr hashchange.zephyr mousewheel mousemove', function (event) {
-    // TODO: Figure out how to limit this animation stop to just the autoscroll
-    $("html, body").stop();
+    viewport.stop_auto_scrolling();
 });
 }());
 /*jslint nomen: false */
diff --git a/zephyr/static/js/viewport.js b/zephyr/static/js/viewport.js
index 9c9ed15b56..c04d821f3c 100644
--- a/zephyr/static/js/viewport.js
+++ b/zephyr/static/js/viewport.js
@@ -4,6 +4,7 @@ var exports = {};
 var jwindow;
 var height;
 var width;
+var in_stoppable_autoscroll = false;
 
 exports.scrollTop = function viewport_scrollTop () {
     return jwindow.scrollTop.apply(jwindow, arguments);
@@ -31,6 +32,46 @@ exports.width = function viewport_width() {
     return width;
 };
 
+
+exports.stop_auto_scrolling = function() {
+    if (in_stoppable_autoscroll) {
+        $("html, body").stop();
+    }
+};
+
+exports.system_initiated_animate_scroll = function (scroll_amount) {
+    suppress_scroll_pointer_update = true; // Gets set to false in the scroll handler.
+    var viewport_offset = exports.scrollTop();
+    in_stoppable_autoscroll = true; 
+    $("html, body").animate({
+        scrollTop: viewport_offset + scroll_amount,
+        always: function () {
+            in_stoppable_autoscroll = false;
+        }
+    });
+};
+
+exports.user_initiated_animate_scroll = function (scroll_amount) {
+    disable_pointer_movement = true;
+    in_stoppable_autoscroll = false; // defensive
+
+    // We use $('html, body') because you can't animate window.scrollTop
+    // on Chrome (http://bugs.jquery.com/ticket/10419).
+    $('html, body').animate({
+        scrollTop: viewport.scrollTop() + scroll_amount
+    }, {
+        complete: function () {
+            // The complete callback is actually called before the
+            // scrolling has completed, so we try to let scrolling
+            // finish before allowing pointer movements again or the
+            // pointer may still move.
+            setTimeout(function () {
+                disable_pointer_movement = false;
+            }, 50);
+        }
+    });
+};
+
 $(function () {
     jwindow = $(window);
     // This handler must be placed before all resize handlers in our application