diff --git a/Developer's-Guide.md b/Developer's-Guide.md
index ac960a3..d3d3427 100644
--- a/Developer's-Guide.md
+++ b/Developer's-Guide.md
@@ -109,10 +109,10 @@ We use [mypy](https://mypy.readthedocs.io/en/stable/) for type checking. Python
 To check for type errors, run:
 
 ```
-mypy game gen
+mypy game
 ```
 
-This only checks the `game` and `gen` packages. `qt_ui` will probably never be checkable because `PySide2` (the Python Qt API) contains many patterns that do not play well with the type checker, but it's good to add the annotations anyway as they help the reader.
+This only checks the `game` package. `qt_ui` will probably never be checkable because `PySide2` (the Python Qt API) contains many patterns that do not play well with the type checker, but it's good to add the annotations anyway as they help the reader.
 
 The type checker is **not** run as part of pre-commit, since that makes it harder to create WIP commits, but is run as a part of the PR and build checks, so it's best to run before uploading a PR, and definitely should be run before a push to develop.