--- a/browser/components/extensions/schemas/windows.json
+++ b/browser/components/extensions/schemas/windows.json
@@ -262,16 +262,18 @@
         "name": "create",
         "type": "function",
         "description": "Creates (opens) a new browser with any optional sizing, position or default URL provided.",
         "async": "callback",
         "parameters": [
           {
             "type": "object",
             "name": "createData",
+            "optional": true,
+            "default": {},
             "properties": {
               "url": {
                 "description": "A URL or array of URLs to open as tabs in the window. Fully-qualified URLs must include a scheme (i.e. 'http://www.google.com', not 'www.google.com'). Relative URLs will be relative to the current page within the extension. Defaults to the New Tab Page.",
                 "optional": true,
                 "choices": [
                   { "type": "string", "format": "relativeUrl" },
                   {
                     "type": "array",

--- a/browser/components/extensions/test/browser/browser_ext_windows_create.js
+++ b/browser/components/extensions/test/browser/browser_ext_windows_create.js
@@ -18,17 +18,19 @@ add_task(function* testWindowCreate() {
       function checkWindow(expected) {
         return new Promise(resolve => {
           _checkWindowPromise = {resolve};
           browser.test.sendMessage("check-window", expected);
         });
       }
 
       async function createWindow(params, expected, keep = false) {
-        let window = await browser.windows.create(params);
+        let window = await browser.windows.create(...params);
+        // params is null when testing create without createData
+        params = params[0] || {};
 
         for (let key of Object.keys(params)) {
           if (key == "state" && os == "mac" && params.state == "normal") {
             // OS-X doesn't have a hard distinction between "normal" and
             // "maximized" states.
             browser.test.assertTrue(window.state == "normal" || window.state == "maximized",
                                     `Expected window.state (currently ${window.state}) to be "normal" but will accept "maximized"`);
           } else {
@@ -49,23 +51,29 @@ add_task(function* testWindowCreate() {
           await browser.windows.update(window.id, {state: "normal"});
         }
         await browser.windows.remove(window.id);
       }
 
       try {
         ({os} = await browser.runtime.getPlatformInfo());
 
-        await createWindow({state: "maximized"}, {state: "STATE_MAXIMIZED"});
-        await createWindow({state: "minimized"}, {state: "STATE_MINIMIZED"});
-        await createWindow({state: "normal"}, {state: "STATE_NORMAL", hiddenChrome: []});
-        await createWindow({state: "fullscreen"}, {state: "STATE_FULLSCREEN"});
+        // Set the current window to state: "normal" because the test is failing on Windows
+        // where the current window is maximized.
+        let currentWindow = await browser.windows.getCurrent();
+        await browser.windows.update(currentWindow.id, {state: "normal"});
+
+        await createWindow([], {state: "STATE_NORMAL"});
+        await createWindow([{state: "maximized"}], {state: "STATE_MAXIMIZED"});
+        await createWindow([{state: "minimized"}], {state: "STATE_MINIMIZED"});
+        await createWindow([{state: "normal"}], {state: "STATE_NORMAL", hiddenChrome: []});
+        await createWindow([{state: "fullscreen"}], {state: "STATE_FULLSCREEN"});
 
         let window = await createWindow(
-          {type: "popup"},
+          [{type: "popup"}],
           {hiddenChrome: ["menubar", "toolbar", "location", "directories", "status", "extrachrome"],
            chromeFlags: ["CHROME_OPENAS_DIALOG"]},
           true);
 
         let tabs = await browser.tabs.query({windowType: "popup", active: true});
 
         browser.test.assertEq(1, tabs.length, "Expected only one popup");
         browser.test.assertEq(window.id, tabs[0].windowId, "Expected new window to be returned in query");