diff -r 2d6691085b8d -r 8d2a026e576b src/Pure/System/session.scala
--- a/src/Pure/System/session.scala	Tue Aug 14 12:21:32 2012 +0200
+++ b/src/Pure/System/session.scala	Tue Aug 14 12:26:02 2012 +0200
@@ -382,7 +382,7 @@
             phase = Session.Startup
 
             // FIXME static init in main constructor
-            val content = Build.session_content(dirs, name)
+            val content = Build.session_content(dirs, name).check_errors
             thy_load.register_thys(content.loaded_theories)
             base_syntax = content.syntax