diff --git a/dumux/porousmediumflow/2pnc/implicit/propertydefaults.hh b/dumux/porousmediumflow/2pnc/implicit/propertydefaults.hh
index 2947aa6477bcc1c11a4591717bbc645214fac9a1..957c7cb3d39e399af37261b4a556751b542afff1 100644
--- a/dumux/porousmediumflow/2pnc/implicit/propertydefaults.hh
+++ b/dumux/porousmediumflow/2pnc/implicit/propertydefaults.hh
@@ -172,6 +172,7 @@ SET_TYPE_PROP(TwoPNC, Indices, TwoPNCIndices <TypeTag, /*PVOffset=*/0>);
 //! Use the ImplicitSpatialParams by default
 SET_TYPE_PROP(TwoPNC, SpatialParams, ImplicitSpatialParams<TypeTag>);
 
+//! Use the model after Millington (1961) for the effective diffusivity
 SET_PROP(TwoPNC, EffectiveDiffusivityModel)
 {
 private :