--- a/devtools/client/aboutdebugging/test/browser_addons_remove.js
+++ b/devtools/client/aboutdebugging/test/browser_addons_remove.js
@@ -23,18 +23,18 @@ add_task(function* removeLegacyExtension
     path: "addons/unpacked/install.rdf",
     name: addonName,
   });
 
   ok(getTargetEl(document, addonID), "add-on is shown");
 
   // Click the remove button and wait for the DOM to change.
   const addonListMutation = waitForMutation(
-    getTemporaryAddonList(document),
-    { childList: true });
+    getTemporaryAddonList(document).parentNode,
+    { childList: true, subtree: true });
   getRemoveButton(document, addonID).click();
   yield addonListMutation;
 
   ok(!getTargetEl(document, addonID), "add-on is not shown");
 
   yield closeAboutDebugging(tab);
 });
 
@@ -52,18 +52,18 @@ add_task(function* removeWebextension() 
     name: addonName,
     isWebExtension: true,
   });
 
   ok(getTargetEl(document, addonID), "add-on is shown");
 
   // Click the remove button and wait for the DOM to change.
   const addonListMutation = waitForMutation(
-    getTemporaryAddonList(document),
-    { childList: true });
+    getTemporaryAddonList(document).parentNode,
+    { childList: true, subtree: true });
   getRemoveButton(document, addonID).click();
   yield addonListMutation;
 
   ok(!getTargetEl(document, addonID), "add-on is not shown");
 
   yield closeAboutDebugging(tab);
 });
 

--- a/devtools/client/aboutdebugging/test/head.js
+++ b/devtools/client/aboutdebugging/test/head.js
@@ -208,17 +208,18 @@ function* installAddon({document, path, 
   let names = [...addonList.querySelectorAll(".target-name")];
   names = names.map(element => element.textContent);
   ok(names.includes(name),
     "The addon name appears in the list of addons: " + names);
 }
 
 function* uninstallAddon({document, id, name}) {
   let addonList = getAddonListWithAddon(document, id);
-  let addonListMutation = waitForMutation(addonList, { childList: true });
+  let addonListMutation = waitForMutation(addonList.parentNode,
+                                          { childList: true, subtree: true });
 
   // Now uninstall this addon
   yield new Promise(done => {
     AddonManager.getAddonByID(id, addon => {
       let listener = {
         onUninstalled: function (uninstalledAddon) {
           if (uninstalledAddon != addon) {
             return;
@@ -228,23 +229,28 @@ function* uninstallAddon({document, id, 
           done();
         }
       };
       AddonManager.addAddonListener(listener);
       addon.uninstall();
     });
   });
 
-  // Ensure that the UI removes the addon from the list
   yield addonListMutation;
-  let names = [...addonList.querySelectorAll(".target-name")];
-  names = names.map(element => element.textContent);
-  ok(!names.includes(name),
-    "After uninstall, the addon name disappears from the list of addons: "
-    + names);
+
+  // If parentNode is none, that means the entire addonList was removed from the
+  // document. This happens when the addon we are removing is the last one.
+  if (addonList.parentNode !== null) {
+    // Ensure that the UI removes the addon from the list
+    let names = [...addonList.querySelectorAll(".target-name")];
+    names = names.map(element => element.textContent);
+    ok(!names.includes(name),
+      "After uninstall, the addon name disappears from the list of addons: "
+      + names);
+  }
 }
 
 /**
  * Returns a promise that will resolve when the add-on list has been updated.
  *
  * @param {Node} document
  * @return {Promise}
  */