diff --git a/utils/novnc_proxy b/utils/novnc_proxy
index 0900f7e..6229dc1 100755
--- a/utils/novnc_proxy
+++ b/utils/novnc_proxy
@@ -1,4 +1,4 @@
-#!/usr/bin/env bash
+#!/bin/sh
 
 # Copyright (C) 2018 The noVNC Authors
 # Licensed under MPL 2.0 or any later version (see LICENSE.txt)
@@ -180,7 +180,7 @@ echo "Starting webserver and WebSockets proxy on port ${PORT}"
 ${WEBSOCKIFY} ${SYSLOG_ARG} ${SSLONLY} --web ${WEB} ${CERT:+--cert ${CERT}} ${KEY:+--key ${KEY}} ${PORT} ${VNC_DEST} ${HEARTBEAT_ARG} ${IDLETIMEOUT_ARG} ${RECORD_ARG} ${TIMEOUT_ARG} &
 proxy_pid="$!"
 sleep 1
-if ! ps -p ${proxy_pid} >/dev/null; then
+if [ -z "$proxy_pid" ] || ! ps -o pid= | grep -qw ${proxy_pid}; then
     proxy_pid=
     echo "Failed to start WebSockets proxy"
     exit 1