diff --git a/syslog-ng/install_check.pl b/syslog-ng/install_check.pl
index 5155e722c..911d1a4ec 100755
--- a/syslog-ng/install_check.pl
+++ b/syslog-ng/install_check.pl
@@ -10,7 +10,7 @@ sub is_installed
 {
 return 0 if (!&get_syslog_ng_version());
 return 0 if (!-r $config{'syslogng_conf'});
-return 1 if ($_[0]);
+return 1 if (!$_[0]);
 return &is_syslog_ng_running() ? 2 : 1;
 }