Undesired Illustration Numbering

I have table of contents based on heading styles (Heading1, Heading2, Heading3). I have numerous illustrations. I want illustrations to number consecutively from beginning of document to end. However, caption numbering restarts at 1 after each use of Heading1. Any help would be appreciated.

Set the cursor immediately in front of a illustration number. Open menu ‘Edit’. The item ‘Fields…’ should be active now, click it. The dialog has a section ‘Numbering by chapter’. Choose ‘none’ from the ‘Level’ drop-down list.