5months old waking 1 hour after bedtime

Does anyone else have the same problem?  My little girl has 2 naps a day, 10.30 and 2.30, she is breastfed and very happy and content, she has never been a poor sleeper.  Over the past week she wakes up just after the hour mark when I put her to bed in the evening, she is inconsolable and needs feeding to calm down. Is this normal? And is there any known cause/solution to this. Thanks Amy