diff --git a/cmake/FindDocBookXML4.cmake b/cmake/FindDocBookXML4.cmake
index 415745f..4d7f089 100644
--- a/cmake/FindDocBookXML4.cmake
+++ b/cmake/FindDocBookXML4.cmake
@@ -34,6 +34,7 @@ function (locate_version version found_dir)
         share/xml/docbook/xml-dtd-${version}
         share/sgml/docbook/xml-dtd-${version}
         share/xml/docbook/${version}
+        opt/docbook/docbook/xml/${version}
     )
 
     find_path (searched_dir docbookx.dtd