using diffplex with StructureMap

[gswartz777]

In our mvc app (.net framework 4.7.2) I'm following along with the example web site by adding the following to our defaultregistry file.

For<ISideBySideDiffBuilder>().Use<SideBySideDiffBuilder>();
For<IDiffer>().Use<Differ>();

But it's complaining about No default Instance is registered and cannot be automatically determined for type 'DiffPlex.IChunker' How can I resolve this in structuremap? Thanks.