--- a/browser/extensions/formautofill/test/browser/browser_manageProfilesDialog.js
+++ b/browser/extensions/formautofill/test/browser/browser_manageProfilesDialog.js
@@ -2,16 +2,18 @@
 
 const TEST_SELECTORS = {
   selAddresses: "#profiles",
   btnRemove: "#remove",
   btnAdd: "#add",
   btnEdit: "#edit",
 };
 
+const DIALOG_SIZE = "width=600,height=400";
+
 function waitForAddresses() {
   return new Promise(resolve => {
     Services.cpmm.addMessageListener("FormAutofill:Addresses", function getResult(result) {
       Services.cpmm.removeMessageListener("FormAutofill:Addresses", getResult);
       // Wait for the next tick for elements to get rendered.
       SimpleTest.executeSoon(resolve.bind(null, result.data));
     });
   });
@@ -40,17 +42,17 @@ add_task(async function test_manageProfi
   });
 });
 
 add_task(async function test_removingSingleAndMultipleProfiles() {
   await saveAddress(TEST_ADDRESS_1);
   await saveAddress(TEST_ADDRESS_2);
   await saveAddress(TEST_ADDRESS_3);
 
-  let win = window.openDialog(MANAGE_PROFILES_DIALOG_URL);
+  let win = window.openDialog(MANAGE_PROFILES_DIALOG_URL, null, DIALOG_SIZE);
   await waitForAddresses();
 
   let selAddresses = win.document.querySelector(TEST_SELECTORS.selAddresses);
   let btnRemove = win.document.querySelector(TEST_SELECTORS.btnRemove);
   let btnEdit = win.document.querySelector(TEST_SELECTORS.btnEdit);
 
   is(selAddresses.length, 3, "Three addresses");
 
@@ -69,17 +71,17 @@ add_task(async function test_removingSin
   EventUtils.synthesizeMouseAtCenter(btnRemove, {}, win);
   await waitForAddresses();
   is(selAddresses.length, 0, "All addresses are removed");
 
   win.close();
 });
 
 add_task(async function test_profilesDialogWatchesStorageChanges() {
-  let win = window.openDialog(MANAGE_PROFILES_DIALOG_URL);
+  let win = window.openDialog(MANAGE_PROFILES_DIALOG_URL, null, DIALOG_SIZE);
   await waitForAddresses();
 
   let selAddresses = win.document.querySelector(TEST_SELECTORS.selAddresses);
 
   await saveAddress(TEST_ADDRESS_1);
   let addresses = await waitForAddresses();
   is(selAddresses.length, 1, "One address is shown");