无法使用Selenium中的CSS选择器选择同级

Selenium WebDriver在尝试使用CSS选择器单击下一个同级元素时抛出InvalidSelectorException。

<div class="checkbox-group">
   <div>     
       <span class="checkbox">::after</span> <!--click on this span makes the checkbox checked-->
       <span class="checkbox-name">Male</span> <!--click on this span doesn't make the checkbox checked-->
   </div>
   <div>
      <span class="checkbox">::after</span>
      <span class="checkbox-name">Female</span>
   </div>
</div>

我的Java代码是:

@FindAll(@FindBy(css=".checkbox-name"))
List<WebElement> checkboxes;

public void selectCheckbox(String value){
    for(WebElement checkbox : checkboxes){
        String text = checkbox.getText();
        if(text.equalsIgnoreCase(value)){
            WebElement control = checkbox.findElement(By.cssSelector("+.checkbox"));//Exception thrown here     
            control.click();
        }
    }
}

org.openqa.selenium.InvalidSelectorException: invalid selector: An invalid or illegal selector was specified. 
** Element info: {Using=css selector, value=+.checkbox}