diff --git a/ipcalc b/ipcalc
index f958f8a..02a7a51 100755
--- a/ipcalc
+++ b/ipcalc
@@ -168,7 +168,11 @@ EOF
    # get netmasks
    if ($ipv6) {
      if (defined $ARGV[1]) {
-	$mask1 = $ARGV[1];
+	$mask1 = check_mask6($ARGV[1]);
+	if ($mask1 == -1) {
+           print "INVALID MASK1\n\n";
+           exit;
+        }
      } else {
         $mask1 = 64;
      }
@@ -199,6 +203,8 @@ EOF
          print set_color($error_color);
       }
       print "$error\n";
+      print set_color($norml_color);
+      exit;
    }
 
 #   print "Address: ".ntoa($address)."\n";
@@ -1089,7 +1095,7 @@ sub ip6ton
 	my $test = $arg;
 	$test =~ s/[0-9a-f:]//g;
 	if ($test ne '') {
-print "Illegal chars\n";
+###print "Illegal chars\n";
 		return -1;
 	}
 	$test = $arg;
@@ -1109,7 +1115,7 @@ print "Illegal chars\n";
 #print "- '$slice'\n";
 		if ($slice eq '') {
 			if ($compressed) {
-print "multiple ::\n";
+###print "multiple ::\n";
 				return -1;
 			}
 			for (my $i=0;$i<8-$#tmp;$i++) {
@@ -1149,6 +1155,15 @@ sub prefixlenton
 	return $n;
 }
 
+sub check_mask6
+{
+   my $mask = shift;
+   if ($mask !~ /^\d{1,3}$/ || $mask < 0 || $mask > 128) {
+      return -1;
+   }
+   return $mask;
+}
+
 sub argton
 # expects 1. an address as dotted decimals, bit-count-mask, or hex
 #         2. netmask flag. if set -> check netmask and negate wildcard
@@ -1188,25 +1203,26 @@ sub argton
    
    # bit-count-mask (24 or /24)
    $arg =~ s/^\/(\d+)$/$1/;
+   # ipv6
+   # for ipv6 this code is never reached:
    if ($ipv6) {
-      if ($arg =~ /^\d{1,3}$/) {
-         if ($arg < 0 || $arg > 128) {
-            return -1;
-         }
-         return prefixlenton($arg);
+      if ($arg !~ /^\d{1,3}$/ || $arg < 0 || $arg > 128) {
+         return -1;
       }
-   } else {
-      if ($arg =~ /^\d{1,2}$/) {
-         if ($arg < 0 || $arg > 32) {
-            return -1;
-         }
-         for ($i=0;$i<$arg;$i++) {
-            $n |= 1 << (31-$i);
-         }
-         return $n;
+      return prefixlenton($arg);
+   } 
+   # ipv4
+   if ($arg =~ /^\d{1,2}$/) {
+      if ($arg < 0 || $arg > 32) {
+         return -1;
       }
+      for ($i=0;$i<$arg;$i++) {
+         $n |= 1 << (31-$i);
+      }
+      return $n;
    }
    
+   
    # hex
    if ($arg =~   /^[0-9A-Fa-f]{8}$/ || 
        $arg =~ /^0x[0-9A-Fa-f]{8}$/  ) {