Permissibility of praying in a garment containing semen

A man wore a garment while he was in a state of ritual purity—Meaning: The man was in a state of ritual purity, but the garment contained semen. He wore it while forgetting about it, and after the prayer, it became clear that there was semen in this garment of which he had not been aware. What is the ruling in this case?
Semen is pure. If a person prays in a garment that contains semen, his prayer is valid, whether he did so intentionally or out of forgetfulness;But say: If it contained urine, and he prayed while forgetting or not knowing, and did not find out until after the prayer, his prayer is valid.