src/Pure/Tools/build.scala

   {
     val build_options = options.int.update("completion_limit", 0).bool.update("ML_statistics", true)
 
     val store = Sessions.store(build_options, system_mode)
 
+    Isabelle_Fonts.init()
+
 
     /* session selection and dependencies */
 
     val full_sessions =
       Sessions.load_structure(build_options, dirs = dirs, select_dirs = select_dirs, infos = infos)