diff -r b904ea8edd73 -r 8dd9df88f647 src/Pure/Isar/parse.scala
--- a/src/Pure/Isar/parse.scala	Wed Apr 30 13:11:24 2014 +0200
+++ b/src/Pure/Isar/parse.scala	Wed Apr 30 22:34:11 2014 +0200
@@ -71,6 +71,8 @@
       atom("file name/path specification", tok => tok.is_name && Path.is_wellformed(tok.content))
     def theory_name: Parser[String] =
       atom("theory name", tok => tok.is_name && Path.is_wellformed(tok.content))
+    def theory_xname: Parser[String] =
+      atom("theory name reference", tok => tok.is_xname && Path.is_wellformed(tok.content))
 
     private def tag_name: Parser[String] =
       atom("tag name", tok =>