TOC formatting in Libreoffice

Hi,

I'm trying to make a table of contents in Libreoffice in this form:

Heading
Heading
1 Heading1
2 Heading1
2.1 Heading2
3 Heading1

Now it looks like this:

Heading
Heading
1Heading1
2Heading1
2.1Heading2
3Heading1


The problem is that I don't know how I could add some space between the numbers and headings (i.e. 1 Heading1, now it's 1Heading1). If I edit the TOC with "Edit Index/Table" > "Entries" and try adding spacec after the number token, the spaces are added before the Headings as well and the TOC looks like this:

_Heading
_Heading
1 Heading1
2 Heading1
2.1 Heading2
3 Heading1
where "_" is an extra not wanted space character.

Can you help?