--- docbook_4/docbook-sgml-4.4/docbook.dcl.~1~	2017-10-17 08:26:00.675876558 +0200
+++ docbook_4/docbook-sgml-4.4/docbook.dcl	2017-10-17 08:26:30.895997614 +0200
@@ -61,8 +61,8 @@
 	NAMING
 		LCNMSTRT ""
 		UCNMSTRT ""
-		LCNMCHAR ".-_"
-		UCNMCHAR ".-_"
+		LCNMCHAR ".-_:"
+		UCNMCHAR ".-_:"
 		NAMECASE
 			GENERAL YES
 			ENTITY  NO