diff -r c0f776b661fa -r f5c2d66faa04 src/Pure/System/session.scala
--- a/src/Pure/System/session.scala	Thu Mar 15 11:37:56 2012 +0100
+++ b/src/Pure/System/session.scala	Thu Mar 15 14:13:49 2012 +0100
@@ -100,8 +100,7 @@
 
         case Text_Edits(name, previous, text_edits, version_result) =>
           val prev = previous.get_finished
-          val syntax = if (prev.is_init) prover_syntax else prev.syntax
-          val (doc_edits, version) = Thy_Syntax.text_edits(syntax, prev, text_edits)
+          val (doc_edits, version) = Thy_Syntax.text_edits(prover_syntax, prev, text_edits)
           version_result.fulfill(version)
           sender ! Change_Node(name, doc_edits, prev, version)