diff --git a/setup-min.sh b/setup-min.sh
index 6ed3305..1ce4c78 100644
--- a/setup-min.sh
+++ b/setup-min.sh
@@ -20,7 +20,7 @@ if [ -z "${PREFIX-}" ]; then
   PREFIX=""
 fi
 
-if [ -n "$NODE_PATH" ]; then
+if [ -n "${NODE_PATH-}" ]; then
   node_install_path=$(dirname $(dirname $NODE_PATH))
 else
   node_install_path=$PREFIX/usr/local