diff --git a/containers/buildkite-windows/start_agent.ps1 b/containers/buildkite-windows/start_agent.ps1
index 4a15ef5..8ac3839 100644
--- a/containers/buildkite-windows/start_agent.ps1
+++ b/containers/buildkite-windows/start_agent.ps1
@@ -1,5 +1,7 @@
 # TODO: remove after migrating scripts to LLVM repo.
 git clone https://github.com/google/llvm-premerge-checks.git c:\llvm-premerge-checks
+# Checkout path is set to a fixed short value (e.g. c:\ws\src) to keep paths
+# short as many tools break on Windows with paths longer than 250.
 $env:BUILDKITE_BUILD_CHECKOUT_PATH = "$env:BUILDKITE_BUILD_PATH\src"
 
 # Install Buildkite agent.