I can’t get AJAX responses working correctly with my login form:

{exp:system_messages:form message_on_success="no"}
    {exp:member:login_form form_class="login_form"}
     <div class="username">
      <label for="username">Username</label><br>
      <input type="text" id="username" class="username" name="username">
     </div>
     <div class="password">
      <label for="password">Password</label><br>
      <input type="password" id="password" class="password" name="password">
     </div>
     {if auto_login}
      <div class="auto_login">
       <input type="checkbox" id="auto_login" name="auto_login" class="auto_login" value="1">Remember me?
      </div>
     {/if}
     <div class="submit-button">
      <input type="submit" name="submit" class="submit" value="Login">
      <div class="clear"></div>
     </div>
     <div class="forgot_password">
      <a href="/forgot-password">Forgot your password?</a>
     </div>
    {/exp:member:login_form}
   {/exp:system_messages:form}

I’m being logged in successfully but it is returning the HTML of the next page, not a JSON response.  Help?

(Attaching a snapshot of my extension settings)