This is with r67651 and related to #4569, #4509 and possibly #4580. >>> from array import array >>> a = array('i', range(16)) >>> m = memoryview(a) >>> a.extend(array('i', range(48))) >>> m[:] = array('i', range(64)) Segmentation fault >>> from array import array >>> a = array('b', range(16)) >>> m = memoryview(a) >>> a.extend(array('b', range(48))) >>> m[:] = array('b', range(64)) Segmentation fault