--- a/devtools/client/netmonitor/test/browser_net_timeline_ticks.js
+++ b/devtools/client/netmonitor/test/browser_net_timeline_ticks.js
@@ -4,17 +4,17 @@
 /**
  * Tests if timeline correctly displays interval divisions.
  */
 
 function test() {
   initNetMonitor(SIMPLE_URL).then(([aTab, aDebuggee, aMonitor]) => {
     info("Starting test... ");
 
-    let { document, L10N, NetMonitorView } = aMonitor.panelWin;
+    let { document, L10N, NetMonitorView, NetMonitorController } = aMonitor.panelWin;
     let { RequestsMenu } = NetMonitorView;
 
     // Disable transferred size column support for this test.
     // Without this, the waterfall only has enough room for one division, which
     // would remove most of the value of this test.
     document.querySelector("#requests-menu-transferred-header-box").hidden = true;
     document.querySelector("#requests-menu-item-template .requests-menu-transferred").hidden = true;
 
@@ -26,16 +26,21 @@ function test() {
       "No tick labels should be displayed when the frontend is opened.");
 
     ok(!RequestsMenu._canvas,
       "No canvas should be created when the frontend is opened.");
     ok(!RequestsMenu._ctx,
       "No 2d context should be created when the frontend is opened.");
 
     waitForNetworkEvents(aMonitor, 1).then(() => {
+      // Make sure the DOMContentLoaded and load markers don't interfere with
+      // this test by removing them and redrawing the waterfall (bug 1224088).
+      NetMonitorController.NetworkEventsHandler.clearMarkers();
+      RequestsMenu._flushWaterfallViews(true);
+
       ok(!document.querySelector("#requests-menu-waterfall-label"),
         "The timeline label should be hidden after the first request.");
       ok(document.querySelectorAll(".requests-menu-timings-division").length >= 3,
         "There should be at least 3 tick labels in the network requests header.");
 
       is(document.querySelectorAll(".requests-menu-timings-division")[0]
         .getAttribute("value"), L10N.getFormatStr("networkMenu.millisecond", 0),
         "The first tick label has an incorrect value");