diff --git a/bin/mpd-monitor b/bin/mpd-monitor
index d477c3e..0b5993d 100755
--- a/bin/mpd-monitor
+++ b/bin/mpd-monitor
@@ -1,7 +1,7 @@
 #!/bin/sh
 
 # quit if another instance is already running
-if [ !$(pidof mpc idleloop > /dev/null) ]; then
+if [ -n "$(pidof mpc idleloop)" ]; then
   echo "mpd-monitor already running"
   exit
 fi