diff --git a/bin/slubsipbuilder.pl b/bin/slubsipbuilder.pl
index 0e30fe97185d6d348b30d700ef109d019e9beb78..0c64680365a0a06321f169e8963c192deaaac77a 100755
--- a/bin/slubsipbuilder.pl
+++ b/bin/slubsipbuilder.pl
@@ -60,8 +60,8 @@ my $man;
 our $VERSION = '1.1';
 GetOptions(
     "IE_directory=s"                => \$directory,                     # required
-    "ppn=s"                         => \$ppn,                           # semi-optional
-    "noppn=s"                       => \$noppn,                         # semi-optional
+    "ppn=s"                         => \$ppn,                           # semi-optional (choice 1 of 2)
+    "noppn=s"                       => \$noppn,                         # semi-optional (choice 2 of 2)
     "SIP_output_path=s"             => \$output,                        # required
     "as_zip"                        => \$as_zip,                        # optional, default: do not zip
     "url=s"                         => \$url,                           # optional, default: SWB Online-Katalog
@@ -78,8 +78,8 @@ GetOptions(
 if ($help)                                  { pod2usage(1); }
 if ($man)                                   { pod2usage(-exitval => 0, -verbose => 2); }
 if (!defined $directory)                    { confess("you need to specify an IE directory, which needs to be archived"); }
-if (!defined $ppn && !defined $noppn)       { confess("you need to specify a PPN, which exists in SWB catalogue"); }
-if (defined $ppn && defined $noppn)         { confess("you can only use '--ppn=foo' or '--noppn=bar'"); }
+if ((defined $ppn) && (defined $noppn))     { confess("you can only specify either -ppn or -noppn"); }
+if ((!defined $ppn) && (!defined $noppn))   { confess("you need to specify a PPN with -ppn or use --noppn"); }
 if (!defined $output)                       { confess("you need to specify an output path, where the SIP will be stored"); }
 if (!defined $url)                          { $url = "http://swb.bsz-bw.de/sru/DB=2.1/username=/password=/";}
 if (!defined $external_conservation_flag)   { $external_conservation_flag="false"; } else { $external_conservation_flag="true"; }