diff --git a/scripts/probe.sh b/scripts/probe.sh
index c85de2f8..150ca636 100644
--- a/scripts/probe.sh
+++ b/scripts/probe.sh
@@ -1,11 +1,14 @@
-#!/bin/bash
+#!/bin/sh
+
+# Please use POSIX Shell
+# https://www.grymoire.com/Unix/Sh.html
 
 IP=127.0.0.1
 PORT=9000
 
 while true; do
     nc -zv ${IP} ${PORT}
-    if [[ "$?" == "0" ]]; then
+    if [ "$?" == "0" ]; then
         exit 0
     fi
     sleep 2