Police are looking for two men who urinated on a rough sleeper before attacking him.
The man was asleep on Holles Street in Grimsby when he awoke to find the two men standing over him at around 3am on 30 March.
As he stood up, they punched and kicked him to the ground.
Humberside Police said the pair fled, leaving the victim needing hospital treatment for injuries to his ribs and collar bone.
The force has released images of two men officers want to find.
A spokesperson said: "A number of lines of enquiry have been investigated and we believe the two men in these CCTV images could assist our enquiries."