[racket] Question about modules

The following two lines trigger an error:

(require (planet dherman/memoize:3:1))
(require (planet soegaard/math:1:4/math))

The error says something along the lines that the soegaard package
requires an older version of the memoize library, and the two can't
coexist.

Shouldn't modules protect me from this?  Shouldn't it be possible for
the math library to use its own required version of the memoize
library, without it screwing up my ability to require the latest
version of the memoize library?

Thanks,

Mark