diff -r 1d2cbcc50fb2 -r 6024353549ca src/Pure/System/session.scala
--- a/src/Pure/System/session.scala	Wed Feb 29 23:31:35 2012 +0100
+++ b/src/Pure/System/session.scala	Thu Mar 01 11:28:33 2012 +0100
@@ -35,7 +35,7 @@
 }
 
 
-class Session(val thy_load: Thy_Load = new Thy_Load)
+class Session(thy_load: Thy_Load = new Thy_Load)
 {
   /* real time parameters */  // FIXME properties or settings (!?)