Error writing values with XML YANG Patch

<yang-patch xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-patch">
<patch-id>test-patch</patch-id>
<comment>this is test patch</comment>
<edit>
    <edit-id>edit1</edit-id>
    <operation>replace</operation>
    <target>/my-leaf11</target>
    <value>
        <my-leaf11>my-leaf11 :: XML value</my-leaf11>
    </value>
</edit>
</yang-patch> 

{
  "errors": {
    "error": [
      {
        "error-tag": "malformed-message",
        "error-message": "Error parsing input: null",
        "error-type": "protocol"
      }
    ]
  }
}