diff --git a/Changes b/Changes
index 38e638f..d1dada9 100644
--- a/Changes
+++ b/Changes
@@ -8,6 +8,7 @@ forgot to remove when adding the Exim support.
   	(thanks to Jean-Marc Didelot, jm.didelot AT teraneo.fr for pointing this out)
 - Fixed to support to show the usage and disk I/O on filesystem names that
   contain spaces. [#234]
+- Fixed to ensure that the 'L' option in port.pm is optional.
 
 
 3.11.0 - 14-Mar-2019
diff --git a/lib/port.pm b/lib/port.pm
index 7c1540a..cbf66f9 100644
--- a/lib/port.pm
+++ b/lib/port.pm
@@ -526,7 +526,7 @@ sub port_cgi {
 
 			# check if the network port is still listening
 			undef(@warning);
-			if(uc($plis) eq "L") {
+			if(uc($plis || "") eq "L") {
 				if($config->{os} eq "Linux") {
 					open(IN, "netstat -nl --$pp |");
 					while(<IN>) {
diff --git a/man/man5/monitorix.conf.5 b/man/man5/monitorix.conf.5
index 2259085..80f68ef 100644
--- a/man/man5/monitorix.conf.5
+++ b/man/man5/monitorix.conf.5
@@ -1995,7 +1995,7 @@ This is the option where each network port specified in \fBlist\fP is described.
 .br
 - the limit value.
 .br
-- the \fIL\fP option which specifies that this port should be listening and Monitorix will advice it, by changing the background color of the graph to red, if finds it down.
+- the \fIL\fP optional option which specifies that this port should be listening and Monitorix will advice it, by changing the background color of the graph to red, if finds it down.
 .RE
 .P
 There is also support (Linux only) for IPv6 network ports activity by using protocol names as \fItcp6\fP or \fIudp6\fP.