diff --git a/LDP/builder/ldp_mk b/LDP/builder/ldp_mk
index b1ee2822..e01a963c 100644
--- a/LDP/builder/ldp_mk
+++ b/LDP/builder/ldp_mk
@@ -90,23 +90,32 @@ if( $s =~ /linuxdoc/i ) {
 
 } else {
 
-    # determine docbook version
-    #
-    ($db_v) = ($s =~ /\s+V(\d)\./i);
-
-    # do not override any various SGML catalog file settings
-    #
     if( $s =~ /\ xml\ /i ) {
         $dtd = 'XML';
         $x   = 'x';
         $dcl = "${_toolroot}/${_jade}/pubtext/xml.dcl";
     }
 
+    # determine docbook version
+    #
+    if( $s =~ /V3\./ ) {
+        $db_v = "3.x";
+        $s = "${_toolroot}/dtd/docbook_31/catalog:";
+    } elsif ( $s =~ /V4\.1/ ) {
+        $db_v = "4.1.2";
+        $s = "${_toolroot}/dtd/docbook${x}_41/catalog:";
+    } elsif ( $s =~ /V4\.2/ ) {
+        $db_v = "4.2";
+        $s = "${_toolroot}/dtd/docbook${x}_42/catalog:";
+    } else {
+        die "\nldp_mk: cannot determine DTD version for $fname\n";
+    }
+
+    # do not override any various SGML catalog file settings
+    #
     if( $ENV{'SGML_CATALOG_FILES'} eq '' ) {
-        $s = ($db_v =~ /3/ ? "${_toolroot}/dtd/docbook${x}_31/catalog:" :
-                             "${_toolroot}/dtd/docbook${x}_41/catalog:")   .
-             "${_toolroot}/dsssl/docbook/catalog:"  .
-             "${_toolroot}/${_jade}/dsssl/catalog";
+        $s .= "${_toolroot}/dsssl/docbook/catalog:"  .
+              "${_toolroot}/${_jade}/dsssl/catalog";
         $ENV{'SGML_CATALOG_FILES'} = $s;
     }
 
@@ -115,7 +124,7 @@ if( $s =~ /linuxdoc/i ) {
     }
 
     $linuxdoc = 0;
-    print "\nldp_mk: $fname is DocBook (vers. $db_v) $dtd\n";
+    print "\nldp_mk: $fname is DocBook (vers. ${db_v}) $dtd\n";
 
     if( $txt_filter eq '' ) {
         $txt_filter = 'w3m';