Fixed table header disappears when the specific height value is removed

Question

I want to create a table with fixed header and vertically scrollable body. Used this solution on stackoverflow (first answer) which works well when there is a specific height value (in this case 200px). But I want my height value to come from my elements parent.

I used height:100%; and height:inherit; under ".scroll tbody" but neither works.

.scroll {
  border: 0;
  border-collapse: collapse;
}

.scroll tr {
  display: flex;
}

.scroll td {
  padding: 3px;
  flex: 1 auto;
  border: 1px solid #aaa;
  width: 1px;
  word-wrap: break;
}

.scroll thead tr:after {
  content: '';
  overflow-y: scroll;
  visibility: hidden;
  height: 0;
}

.scroll thead th {
  flex: 1 auto;
  display: block;
  border: 1px solid #000;
}

.scroll tbody {
  display: block;
  width: 100%;
  overflow-y: auto;
  height: 200px;
}

<table class="scroll" width="400px">
  <thead>
    <tr>
      <th>Header</th>
      <th>Header</th>
      <th>Header</th>
      <th>Header</th>
      <th>Header</th>
      <th>Header</th>
    </tr>
  </thead>
  <tr>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
  </tr>
  <tr>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
  </tr>
  <tr>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
  </tr>
  <tr>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
  </tr>
  <tr>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
  </tr>
  <tr>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
  </tr>
  <tr>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
  </tr>
  <tr>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
  </tr>
  <tr>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
  </tr>
  <tr>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
  </tr>
  <tr>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
  </tr>
  <tr>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
  </tr>
  <tr>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
  </tr>
  <tr>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
  </tr>
  <tr>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
  </tr>
  <tr>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
  </tr>
  <tr>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
  </tr>
  <tr>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
    <td>Data</td>
  </tr>
</table>