How can I stop my dogs scent marking their beds?

I have two young male pugs who are house-trained except that occasionally they will pee on their beds in their own room. I have attributed this to scent marking and it means I cannot put blankets in their beds without them ruining them! They do not do this anywhere else in the house or in my presence, only when... show more I have two young male pugs who are house-trained except that occasionally they will pee on their beds in their own room. I have attributed this to scent marking and it means I cannot put blankets in their beds without them ruining them! They do not do this anywhere else in the house or in my presence, only when they are on their own, so I cannot train them otherwise. They get along fine and aren't competitive and they don't even do it elsewhere in their room. Is there anything I can buy or do to stop them doing this?

PS. Please don't suggest neutering as an answer as this is not an option and they do not display any aggressive behaviour, humping or scenting elsewhere.
Update: I am asking for constructive solutions so passing comment on how I treat my dogs is not helpful. They are loved, fussed, spoilt, get plenty of exercise and care and love eachother. This happens when I / they go to bed at night (after being let outside to do toilet) and inevitably have to be left by themselves!... show more I am asking for constructive solutions so passing comment on how I treat my dogs is not helpful. They are loved, fussed, spoilt, get plenty of exercise and care and love eachother. This happens when I / they go to bed at night (after being let outside to do toilet) and inevitably have to be left by themselves! (Much as I would like to be with them 24/7).
Update 2: To clarify, they do get taken out by either myself or my husband at night UNTIL they do their business. And they aren't really small puppies any more, one is ten months and the other fifteen months, hence them both being fully house trained. Thanks for answers so far, I'm thinking the feeding in bed... show more To clarify, they do get taken out by either myself or my husband at night UNTIL they do their business. And they aren't really small puppies any more, one is ten months and the other fifteen months, hence them both being fully house trained. Thanks for answers so far, I'm thinking the feeding in bed solution is a good one. Keep the answers coming please!
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