How can i use nightwatch with async/await functionality?

i m using nightwatch testing framework to test some functionality of the <input />, and it fails on a race issue.

What i need to test

1. Add a value to the input text: xxxx.
2. press backspace 4 times.
3. assert that the input has value ''.

But i get that the input has value of xx:

ERROR: Expected element <#inputElement> to have value equal: "" - expected "equal ''" but got: "xx"

    "type 4 chars and use backspace to clear the input": browser => {
    searchBox.waitForElementVisible("@input")
    .click("@input")
    .setValue("@input",'xxxx');
    for (let i = 0; i < 4; i++) {
        await browser.keys(browser.Keys.BACK_SPACE);
    }
    searchbox.expect.element("@input").value.to.equal("");

    searchbox.click("@input");
 searchbox.expect.element("@input").value.to.equal("");
 browser.end(); 
},

This leads to the conclusion, that the for loop is executed before the input gets cleared, and then moves forward to the assertion. I tried the same test with async/await but i have the same error again. Do i miss something ?

I test it with async/await like so:

    "type 4 chars and use backspace to clear the input": async browser => {
    searchBox.waitForElementVisible("@input")
    .click("@input")
    .setValue("@input",'xxxx');
    for (let i = 0; i < 4; i++) {
        await browser.keys(browser.Keys.BACK_SPACE);
    }

    await searchbox.click("@input");
    await searchbox.expect.element("@input").value.to.equal("");
    await browser.end(); 
},

Any help is welcome.