This study concerns differences in the perception of phonemes that have undergone near merger within the past few generations in the Copenhagen speech community. It is hypothesized that this process can lead to a difference in phoneme boundaries across generations. We studied the effect of speaker and listener age on the placement of the phoneme boundary between /ɛ/ and /a/ in Copenhagen Danish using a forced choice word identification task. The results show that younger listeners accept a greater range of vowels as tokens of /a/ in accordance with the changes in production of this phoneme.