diff --git a/dom/events/test/pointerevents/test_pointerevent_capture_suppressing_mouse-manual.html b/dom/events/test/pointerevents/test_pointerevent_capture_suppressing_mouse-manual.html
index dc39035922..5eb631f6a0 100644
--- a/dom/events/test/pointerevents/test_pointerevent_capture_suppressing_mouse-manual.html
+++ b/dom/events/test/pointerevents/test_pointerevent_capture_suppressing_mouse-manual.html
@@ -19,7 +19,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=1000870
       function executeTest(int_win) {
         sendMouseEvent(int_win, "target0",    "mousemove");
         sendMouseEvent(int_win, "target1",    "mousemove");
-        sendMouseEvent(int_win, "btnCapture", "mousedown", {button:1});
+        sendMouseEvent(int_win, "btnCapture", "mousedown");
         sendMouseEvent(int_win, "target1",    "mousemove");
         sendMouseEvent(int_win, "target0",    "mousemove");
         sendMouseEvent(int_win, "target1",    "mousemove");