Index: maven-xdoc.dtd
===================================================================
--- maven-xdoc.dtd	(revision 390385)
+++ maven-xdoc.dtd	(working copy)
@@ -1208,6 +1208,9 @@
 
 <!ELEMENT escapeXml ANY>
 <!ELEMENT source %block.source;>
+<!ATTLIST source
+  xml:space   (preserve)     #FIXED 'preserve'
+  >
 
 <!ELEMENT section %block.section;>
 <!ATTLIST section