diff --git a/xdoc/src/dtd/maven-xdoc-1.10.dtd b/xdoc/src/dtd/maven-xdoc-1.10.dtd
index 98865302..056bbe09 100644
--- a/xdoc/src/dtd/maven-xdoc-1.10.dtd
+++ b/xdoc/src/dtd/maven-xdoc-1.10.dtd
@@ -1208,6 +1208,9 @@ several semantically related columns together.
 
 <!ELEMENT escapeXml ANY>
 <!ELEMENT source %block.source;>
+<!ATTLIST source
+  xml:space   (preserve)     #FIXED 'preserve'
+  >
 
 <!ELEMENT section %block.section;>
 <!ATTLIST section
diff --git a/xdoc/src/plugin-resources/dtd/maven-xdoc.dtd b/xdoc/src/plugin-resources/dtd/maven-xdoc.dtd
index 98865302..056bbe09 100644
--- a/xdoc/src/plugin-resources/dtd/maven-xdoc.dtd
+++ b/xdoc/src/plugin-resources/dtd/maven-xdoc.dtd
@@ -1208,6 +1208,9 @@ several semantically related columns together.
 
 <!ELEMENT escapeXml ANY>
 <!ELEMENT source %block.source;>
+<!ATTLIST source
+  xml:space   (preserve)     #FIXED 'preserve'
+  >
 
 <!ELEMENT section %block.section;>
 <!ATTLIST section