src/Pure/PIDE/document.scala

       val edits: List[Node.Edit[Text.Edit, Text.Perspective]] =
         get_blob match {
           case None =>
             List(
               Node.Deps(
-                if (session.resources.base.loaded_theory(node_name))
+                if (session.resources.session_base.loaded_theory(node_name))
                   node_header.error("Cannot update finished theory " + quote(node_name.theory))
                 else node_header),
               Node.Edits(text_edits), perspective)
           case Some(blob) => List(Node.Blob(blob), Node.Edits(text_edits))
         }