Elm History Export Bug

For some reason, this minimal setup for a counter program is experiencing a bug with Elm's debug history exports. Compiled with either elm-make or with webpack, clicking the counter buttons a few times and then exporting the history yields malform data like so:

{"$":0,"a":{"metadata":{"versions":{"elm":"0.19.0"},"types":{"message":"Main.Msg","aliases":{},"unions":{"Main.Msg":{"args":[],"tags":{"Decrement":[],"Increment":[],"UpdateSecretField":["String.String"]}},"String.String":{"args":[],"tags":{"String":[]}}}}},"history":[null,null,null,null,null]}}

The export works fine for @rtfeldman's Elm SPA example, so it must be something subtle about this code, but for the life of me I can't figure it out.

Expected: the history field contains data about the messages that have been received

Actual: each entry is null.

Steps to reproduce:

1. Install Elm/etc. by running yarn install (or npm if you want)
2. yarn run elm make --debug --output index.html Main.elm
3. open index.html in whatever browser you want
4. Click some buttons
5. Export history and view the resulting JSON data

You can also test this against webpack:

1. Install Elm as above
2. Run yarn server
3. Trigger actions and view the history data as above