  It is argued that the definition of the twist-3 transverse momentum dependent
correlation functions must be modified if they contain light-like Wilson lines.
In the framework of a simple spectator model of the nucleon we show explicitly
the presence of a light-cone divergence for a specific twist-3 time-reversal
odd parton density. This divergence emerges for all eight twist-3 T-odd
correlators and appears also in the case of a quark target in perturbative QCD.
The divergence can be removed by using non-light-like Wilson lines. Based on
our results we argue that currently there exists no established factorization
formula for transverse momentum dependent twist-3 observables in semi-inclusive
DIS and related processes.
