diff --git a/README.md b/README.md
index 792148f..2b248d7 100644
--- a/README.md
+++ b/README.md
@@ -95,7 +95,13 @@ inputs from the `codegen` program. Commonly used variables are:
 
 ## Running `codegen`
 
-The easiest way to run `codegen` is via `cargo`:
+The easiest way to run `codegen` on a clone of the glam repo is to first initialize the submodule with `git`:
+
+```sh
+git submodule init
+```
+
+Then run it via `cargo`:
 
 ```sh
 cargo run -p codegen