src/Pure/term.ML

--- a/src/Pure/term.ML	Fri Jul 12 13:12:21 2013 +0200
+++ b/src/Pure/term.ML	Wed Jul 10 16:25:26 2013 +0200
@@ -980,6 +980,7 @@
       (case rev (Symbol.explode x) of
         _ :: "\\<^sub>" :: _ => false
       | _ :: "\\<^isub>" :: _ => false
+      | _ :: "\\<^sup>" :: _ => false
       | _ :: "\\<^isup>" :: _ => false
       | c :: _ => Symbol.is_digit c
       | _ => true);