truecrypt 7.1a requires 10.4 or later on Yosemite 10.10

After reading articles about the state of Truecrypt in February 2015, I decided to download the last stable version of Truecrypt that allows full usage of Truecrypt: that is, version 7.1a

7.2 version that can only be used to view, but no longer to create new, TrueCrypt volumes.

see http://ift.tt/1ppXYYa

I then proceeded to install this on my Mac, running on Yosemite 10.10

But I got the error message "truecrypt 7.1a requires 10.4 or later", see below.

I guess it's simply a schoolboy error from a developer of the Truecrypt team, as it considers 10.4 being above 10.10, or maybe it's rather Apple who messed up & should have consistantly used 2 digits after the dot (i.e. use 10.04 rather than 10.4).

In any case, I find myself unable to install Truecrypt. Anyone found a solution for this?