--- a/src/Pure/Isar/outer_syntax.scala Wed Nov 01 18:37:49 2017 +0100
+++ b/src/Pure/Isar/outer_syntax.scala Wed Nov 01 20:46:23 2017 +0100
@@ -112,7 +112,8 @@
val keywords1 = keywords ++ other.keywords
val completion1 = completion ++ other.completion
val rev_abbrevs1 = Library.merge(rev_abbrevs, other.rev_abbrevs)
- if ((keywords eq keywords1) && (completion eq completion1)) this
+ if ((keywords eq keywords1) && (completion eq completion1) && (rev_abbrevs eq rev_abbrevs1))
+ this
else new Outer_Syntax(keywords1, completion1, rev_abbrevs1, language_context, has_tokens)
}