Sticky white tape to prevent light getting in at edge of blinds and curtains

[johnbuoy]

The slightest amount of light wakes up my son. I've got a black out roller blind and black out lined curtains but a tiny amount of light still gets through at the top and sides. Is there some sticky white tape an inch or two thick that I could stick to the window to prevent this?
Thanks.

We used strips of velcro, one side stuck on to the window frame, the other side sewn onto the blackout curtain.

Second the Velcro - you can get white or black and it works well.