Do you actually need to access it?
If your code is <64K, then it doesn't matter!
These days, ROMs >64K are often no more expensive (even cheaper) than ROMs 64K or less - so it can be worthwhile buying a bigger ROM and only using 64K of it!

On the other hand, if you're starting out with the intention of writing code bigger than 64K, you should seriously consider whether an 8051 with 16 address bits is a sensible processor to use - especially without prior experience of banking (aka "paging")