diff --git a/IP.pm b/IP.pm
index 1119f9e..8a845df 100644
--- a/IP.pm
+++ b/IP.pm
@@ -139,7 +139,7 @@
 				#############################################
 
 
-our $VERSION = '3.07';
+our $VERSION = '3.08';
 
 # Preloaded methods go here.
 
@@ -258,6 +258,19 @@
 	vec($bmask, 3, 8) = 0;
     }
     elsif ($mask =~ m/^(\d+)\.(\d+)\.(\d+)\.(\d+)$/) {
+
+	for my $i ($1, $2, $3, $4) {
+	    return undef 
+		unless grep { $i == $_ }
+	    (255, 254, 252, 248, 224, 192, 160, 128, 0);
+	}
+
+	return undef if ($1 < $2 or $2 < $3 or $3 < $4);
+	
+	return undef if $2 != 0 and $1 != 255;
+	return undef if $3 != 0 and $2 != 255;
+	return undef if $4 != 0 and $3 != 255;
+					   
 	vec($bmask, 0, 8) = $1;
 	vec($bmask, 1, 8) = $2;
 	vec($bmask, 2, 8) = $3;
@@ -485,13 +498,16 @@
 
     if (defined $_[2]) {
 	$mask 		= _parse_mask $_[2], 32;
+	return undef unless defined $mask;
     }
     elsif (defined $mask) {
 	$mask 		= _parse_mask $mask, 32;
+	return undef unless defined $mask;
     }
     else {
 	$hasmask	= 0;
 	$mask 		= _parse_mask 32, 32;
+	return undef unless defined $mask;
     }
 
     my $self = _v4($ip, $mask, $hasmask);
@@ -850,6 +866,7 @@
 }
 
 1;
+
 __END__
 
 =head1 NAME
@@ -1435,6 +1452,17 @@
 
 =back
 
+=item 3.08
+
+=over
+
+=item *
+
+By popular request, C<-E<gt>new()> now checks the sanity of the netmasks
+it receives. If the netmask is invalid, C<undef> will be returned.
+
+=back
+
 =back
 
 =head1 AUTHOR
diff --git a/MANIFEST b/MANIFEST
index 4c344b8..594627c 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -16,6 +16,7 @@
 t/v4-cidr.t
 t/over-arr.t
 t/v4-range.t
+t/v4-badnm.t
 t/v4-basem.t
 t/v4-first.t
 t/wildcard.t
diff --git a/README b/README
index 2bbb5f2..fc5f4ef 100644
--- a/README
+++ b/README
@@ -1,5 +1,7 @@
 NetAddr::IP - Manages IPv4 (your traditional IP) addresses and subnets
 
+     * * * * THIS MODULE REQUIRES PERL 5.6.0 OR NEWER. * * * *
+
 This  module  is  designed as  a  help  for  managing (ranges  of)  IP
 addresses. It includes efficient implementations for most common tasks
 done  to subnets or  ranges of  IP addresses,  namely verifying  if an
diff --git a/t/v4-badnm.t b/t/v4-badnm.t
new file mode 100644
index 0000000..a69da61
--- /dev/null
+++ b/t/v4-badnm.t
@@ -0,0 +1,56 @@
+# I know this does not look like -*- perl -*-, but I swear it is...
+
+use NetAddr::IP;
+use strict;
+
+$| = 1;
+
+our @badnets = (
+		'10.10.10.10/255.255.0.255',
+		'10.10.10.10/255.0.255.255',
+		'10.10.10.10/0.255.255.255',
+		'10.10.10.10/128.255.0.255',
+		'10.10.10.10/255.128.0.255',
+		'10.10.10.10/255.255.255.129',
+		'10.10.10.10/255.255.129.0',
+		'10.10.10.10/255.255.255.130',
+		'10.10.10.10/255.255.130.0',
+		'10.10.10.10/255.0.0.1',
+		'10.10.10.10/255.129.0.1',
+		'10.10.10.10/0.255.0.255',
+		);
+
+our @goodnets = ();
+
+push @goodnets, "10.0.0.1/$_" for (0 .. 32);
+push @goodnets, "10.0.0.1/255.255.255.255";
+
+print '1..', (scalar @badnets + scalar @goodnets) , "\n";
+
+my $count = 1;
+
+for my $bad (@badnets) {
+
+    if (defined NetAddr::IP->new($bad)) {
+	print "not ok $count # $bad should fail but succeeded\n";
+    }
+    else {
+	print "ok $count # $bad must fail\n";
+    }
+
+    ++ $count;
+}
+
+for my $good (@goodnets) {
+
+    if (defined NetAddr::IP->new($good)) {
+	print "ok $count # $good should not fail\n";
+    }
+    else {
+	print "not ok $count # $good must not fail\n";
+    }
+
+    ++ $count;
+}
+
+