diff --git a/calendar/base/content/calendar-task-tree.xml b/calendar/base/content/calendar-task-tree.xml
index b90a74709f..604a4966db 100644
--- a/calendar/base/content/calendar-task-tree.xml
+++ b/calendar/base/content/calendar-task-tree.xml
@@ -212,19 +212,19 @@
       <field name="mTaskArray">[]</field>
       <field name="mHash2Index"><![CDATA[({})]]></field>
       <field name="mPendingRefreshJobs"><![CDATA[({})]]></field>
-        <field name="mShowCompletedTasks">true</field>
-        <field name="mFilter">null</field>
-        <field name="mStartDate">null</field>
-        <field name="mEndDate">null</field>
-        <field name="mDateRangeFilter">null</field>
-        <field name="mTextFilterField">null</field>
+      <field name="mShowCompletedTasks">true</field>
+      <field name="mFilter">null</field>
+      <field name="mStartDate">null</field>
+      <field name="mEndDate">null</field>
+      <field name="mDateRangeFilter">null</field>
+      <field name="mTextFilterField">null</field>
 
-        <property name="currentIndex">
-          <getter><![CDATA[
-            let tree = document.getAnonymousElementByAttribute(
-                this, "anonid", "calendar-task-tree");
-            return tree.currentIndex;
-        ]]></getter>
+      <property name="currentIndex">
+        <getter><![CDATA[
+          let tree = document.getAnonymousElementByAttribute(
+              this, "anonid", "calendar-task-tree");
+          return tree.currentIndex;
+      ]]></getter>
       </property>
 
       <property name="currentTask">
@@ -319,6 +319,7 @@
             return null;
         ]]></body>
       </method>
+
       <method name="getTaskAtRow">
         <parameter name="aRow"/>
         <body><![CDATA[
@@ -773,13 +774,14 @@
              */
 
             _getItemFromEvent: function(event, aCol, aRow) {
-                aRow = aRow || {};
-                let childElt = {};
-                this.treebox.getCellAt(event.clientX, event.clientY, aRow, aCol || {}, childElt);
-                if (!childElt.value) {
-                    return false;
+                let { col, row } = this.treebox.getCellAt(event.clientX, event.clientY);
+                if (aCol) {
+                    aCol.value = col;
                 }
-                return aRow && aRow.value > -1 && this.binding.mTaskArray[aRow.value];
+                if (aRow) {
+                    aRow.value = row;
+                }
+                return row > -1 && this.binding.mTaskArray[row];
             },
 
             // Helper function to display datetimes
diff --git a/calendar/test/mozmill/views/testTaskView.js b/calendar/test/mozmill/views/testTaskView.js
index 9b750b22a0..6ce2c8b659 100755
--- a/calendar/test/mozmill/views/testTaskView.js
+++ b/calendar/test/mozmill/views/testTaskView.js
@@ -37,7 +37,6 @@ function setupModule(module) {
 
 // Mozmill doesn't support trees yet, therefore completed checkbox and line-through style are not
 // checked.
-testTaskView.__force_skip__ = true;
 function testTaskView() {
     // paths
     let treeChildren = `
@@ -65,7 +64,7 @@ function testTaskView() {
     }
 
     let taskTreeNode = lookup(taskTree).getNode();
-    let countBefore = taskTreeNode.mTaskArray.length;
+    controller.assert(() => taskTreeNode.mTaskArray.length == 0);
 
     // Add task.
     let taskInput= lookup(`
@@ -76,11 +75,7 @@ function testTaskView() {
     controller.keypress(taskInput, "VK_RETURN", {});
 
     // Verify added.
-    let countAfter;
-    controller.waitFor(() => {
-        countAfter = taskTreeNode.mTaskArray.length;
-        return countAfter == (countBefore + 1);
-    }, "Added Task did not appear; countBefore=" + countBefore + ", countAfter=" + countAfter);
+    controller.waitFor(() => taskTreeNode.mTaskArray.length == 1, "Added Task did not appear");
 
     // Last added task is automatically selected so verify detail window data.
     controller.assertJSProperty(eid("calendar-task-details-title"), "textContent", TITLE);
@@ -106,6 +101,9 @@ function testTaskView() {
         task.click(taskid("button-saveandclose"));
     });
 
+    controller.assert(() => taskTreeNode.mTaskArray.length < 2, "Task added but should not have been");
+    controller.assert(() => taskTreeNode.mTaskArray.length > 0, "Task removed but should not have been");
+
     // Verify description and status in details pane.
     controller.assertValue(lookup(`
         ${TASK_VIEW}/{"flex":"1"}/id("calendar-task-details-container")/
@@ -158,10 +156,7 @@ function testTaskView() {
     // Delete task and verify.
     countBefore = taskTreeNode.mTaskArray.length;
     controller.click(eid("calendar-delete-task-button"));
-    controller.waitFor(() => {
-        countAfter = taskTreeNode.mTaskArray.length;
-        return countAfter == (countBefore - 1);
-    }, "Task did not delete; countBefore=" + countBefore + ", countAfter=" + countAfter);
+    controller.waitFor(() => taskTreeNode.mTaskArray.length == 0, "Task did not delete");
 }
 
 function teardownTest(module) {
