pt-table-checksum: diffs on float columns between master 5.1 and slaves 5.5

Hello,
we are using pt-table-checksum 2.2.16 and we have diffs when checksumming tables with float columns; our setup is a master running mysql 5.1 and slaves running 5.5 .

we found https://blueprints.launchpad.net/percona-toolkit/+spec/pt-table-checksum–floating-point-notation and tried that patch, but the issue is still not solved.

we are sure that the problem is in that area, as if we skip all the float values, then we see 0 diffs.

can someone help us fix this?

thanks!!