diff --git a/main.sh b/main.sh
index 13b052cb..f996e3e9 100755
--- a/main.sh
+++ b/main.sh
@@ -364,6 +364,8 @@ for tool in "${tools[@]}"; do
             # https://nexte.st/book/pre-built-binaries.html
             case "${OSTYPE}" in
                 linux*)
+                    # musl build of nextest is slow, so use glibc build if host_env is gnu.
+                    # https://github.com/taiki-e/install-action/issues/13
                     case "${host_env}" in
                         gnu) url="https://get.nexte.st/${version}/linux" ;;
                         *) url="https://get.nexte.st/${version}/linux-musl" ;;