diff --git a/README.adoc b/README.adoc
index a17d1d5..a7b36ad 100644
--- a/README.adoc
+++ b/README.adoc
@@ -232,6 +232,8 @@ and then rebuild the kernel modules and re-run to see it take effect:
 
 Congratulations, you are now officially a kernel module hacker!
 
+We use `./build-buildroot` here because kernel modules go into the root filesystem, and it is Buildroot that generates our root filesystem. The kernel modules are inside a Buildroot package.
+
 The reboot after rebuild is annoying. We don't have a perfect solution for it yet, but there are some ideas cooking at: <<gem5-restore-new-script>>.
 
 Not satisfied with kernel modules? OK then, let's hack up the <<linux-kernel-entry-point,entry point of the>> Linux kernel itself.