How to set class attribute on vuejs functional component

I have a vuejs functional component that mimics a div behavior. To do so, I set it's class based on the props that it receives.

Something like this:

<MyDiv textAlign="left">Div with left aligned text</MyDiv>

Becomes:

<div class="text-left">Div with left aligned text</div>

However, if MyDiv component is the root element for some other component, like:

Card.vue

<template>
  <MyDiv display="inline-block" textAlign="center">
    <slot />
  </MyDiv>
</template>

And if Card receive any class attribute when used, I can't set the class attribute value based on MyDiv props, instead, class (on MyDiv) is overridden by the class received by Card.

So this:

<Card class="cool-style">Card content</Card>

Becomes:

<div class="cool-style">Card content</div>

Ant not this (what I need):

<div class="cool-style inline-block text-center">Card content</div>

Here's MyDiv component:

MyDiv.vue

export default {
  name: 'my-div',
  functional: true,
  props: {
    textAlign: {
      type: String,
      allowed: ['left', 'right', 'center'],
      default: null
    },
    display: {
      type: String,
      allowed: ['hidden', 'block', 'inline-block', 'flex'],
      default: null
    }
  },
  render: function(createElement, context) {
    let classes = [];

    // Adds parent class to itself
    if (typeof context.data.staticClass == 'string') {
      classes.push(context.data.staticClass);
    }

    let classes = classes.concat([
      'my-div',
      context.props.textAlign && `text-${context.props.textAlign}`,
      context.props.display && context.props.display
    ]);

    classes = classes.filter(elm => elm != null);
    classes = classes.join(' ').trim();

    return createElement(
      props.type,
      {
        attrs: {
          class: classes
        }
      },
      context.children
    );
  }
};

TL;DR

How can I force my custom class to a vue functional component, when it's parent have already a class being set?

As a side note, it can be done using statefull (non-functional and regular) components.