Start Page extension not working in Incognito Mode

[sa4zet]

I set New Tab Page to Start Page and checked Controlled by Extension.
In normal mode this is working fine.
But in Incognito Mode it's not working. Does not shows the Start Page, just a blank page.
Yes the extension allowed in Incognito Mode and successfully loaded (I can see the extension button).

• Vivaldi 3.5.2115.73 (Stable channel) (64-bit)
• Revision cb5b3c147056f37fd09f1442d1231225fd8bfb24
• OS Linux