diff --git a/pkgs/servers/irker/default.nix b/pkgs/servers/irker/default.nix
index 6ad233593a3b..002760ff0fd3 100644
--- a/pkgs/servers/irker/default.nix
+++ b/pkgs/servers/irker/default.nix
@@ -12,7 +12,7 @@ stdenv.mkDerivation rec {
     sha256 = "1hslwqa0gqsnl3l6hd5hxpn0wlachxd51infifhlwhyhd6iwgx8p";
   };
 
-  nativeBuildInputs = [ pkgconfig xmlto docbook2x ];
+  nativeBuildInputs = [ pkgconfig xmlto docbook2x docbook_xsl docbook_xml_dtd_412 ];
 
   buildInputs = [
     python
@@ -21,10 +21,6 @@ stdenv.mkDerivation rec {
     # python.pkgs.pysocks
   ];
 
-  preBuild = ''
-    export XML_CATALOG_FILES='${docbook_xsl}/xml/xsl/docbook/catalog.xml ${docbook_xml_dtd_412}/xml/dtd/docbook/catalog.xml'
-  '';
-
   postPatch = ''
     substituteInPlace Makefile \
       --replace '-o 0 -g 0' ""