diff --git a/ipcalc b/ipcalc
index 52be4ae..3866b33 100755
--- a/ipcalc
+++ b/ipcalc
@@ -22,7 +22,7 @@
 use strict;
 use bignum;
 
-my $version = '0.51';
+my $version = '0.52';
 
 my @class   = qw (0 8 16 24 4 5 5);
 
diff --git a/ipcalc.cgi b/ipcalc.cgi
index de6a1d1..d6d09ed 100755
--- a/ipcalc.cgi
+++ b/ipcalc.cgi
@@ -65,6 +65,12 @@ if (! defined $host) {
 	$host = '';
 }
 
+@mask0 = split(/\//, $host);
+if (@mask0[1] ne "") {
+  $host = @mask0[0];
+  $mask1 = @mask0[1];
+}
+
 if (! defined $mask1) {
 	$mask1 = '';
 	$help = 1;