src/Tools/jEdit/src/plugin.scala

         case msg: EditorStarted =>
           PIDE.session.start("Isabelle", Isabelle_Logic.session_args())
 
           if (Distribution.is_identified && !Distribution.is_official) {
             GUI.warning_dialog(jEdit.getActiveView, "Isabelle version for testing",
-              "This is " + Distribution.version +".",
+              "This is " + Distribution.version + ".",
               "It is for testing only, not for production use.")
           }
 
         case msg: BufferUpdate
         if msg.getWhat == BufferUpdate.LOADED ||