diff -r 49501dc1a7b8 -r 05641edb5d30 src/Pure/Thy/thy_syntax.scala
--- a/src/Pure/Thy/thy_syntax.scala	Sat Aug 13 16:07:26 2011 +0200
+++ b/src/Pure/Thy/thy_syntax.scala	Sat Aug 13 20:20:36 2011 +0200
@@ -179,8 +179,8 @@
       var nodes = previous.nodes
 
       edits foreach {
-        case (name, Document.Node.Remove()) =>
-          doc_edits += (name -> Document.Node.Remove())
+        case (name, Document.Node.Clear()) =>
+          doc_edits += (name -> Document.Node.Clear())
           nodes -= name
 
         case (name, Document.Node.Edits(text_edits)) =>