We have just upgraded to hibernate-validator 5.x (from 4.x).
One of our IT fails with the following email:
In this case the call to toAscii is broken down in two cycles:
The last cycle will throw an IllegalArgumentException( "Empty label is not a legal name") in IDN.toASCIIInternal
Failing test case:
I guess this was broken in where some of the code was rewritten by @hardy.ferentschik