I've made two groups named manager and approver. But when I select manager and save, it's saved as approver. This is my xml. What am I doing wrong?

<?xml version="1.0" encoding="utf-8"?>
<odoo>

<record model="ir.module.category" id="document_approve_demo.module_category_approval">
<field name="name">Document Demo</field>
<field name="sequence">100</field>
</record>

<record id="group_approval_approver" model="res.groups">
<field name="name">Approver</field>
<field name="category_id" ref="document_approve_demo.module_category_approval"/>
<field name="implied_ids" eval="[(4, ref('base.group_user'))]"/>
</record>

<record id="group_approval_manager" model="res.groups">
<field name="name">Manager</field>
<field name="category_id" ref="document_approve_demo.module_category_approval"/>
<field name="implied_ids" eval="[(4, ref('group_approval_approver'))]"/>
</record>

</odoo>

EDIT: The code is right, when I tried it on a different database, it worked.