diff -r 60e7072b8dbe -r 41f80c6978bc src/Pure/PIDE/rendering.scala
--- a/src/Pure/PIDE/rendering.scala	Mon Mar 06 17:10:37 2017 +0100
+++ b/src/Pure/PIDE/rendering.scala	Mon Mar 06 17:48:22 2017 +0100
@@ -76,7 +76,8 @@
     Markup.LEGACY -> legacy_pri,
     Markup.LEGACY_MESSAGE -> legacy_pri,
     Markup.ERROR -> error_pri,
-    Markup.ERROR_MESSAGE -> error_pri)
+    Markup.ERROR_MESSAGE -> error_pri
+  ).withDefaultValue(0)
 
   val message_underline_color = Map(
     writeln_pri -> Color.writeln,