oops;

--- a/src/Pure/Thy/thy_syn.ML	Wed Aug 06 11:52:16 1997 +0200
+++ b/src/Pure/Thy/thy_syn.ML	Wed Aug 06 11:56:31 1997 +0200
@@ -30,7 +30,7 @@
 (* augment syntax *)
 
 fun add_syntax keys sects =
- (keywords := keys union ! keywords;
+ (keywords := (keys union ! keywords);
   sections := sects @ ! sections;
   syntax := make_syntax ());