src/Pure/Thy/export_theory.ML

--- a/src/Pure/Thy/export_theory.ML	Sun May 20 15:28:59 2018 +0200
+++ b/src/Pure/Thy/export_theory.ML	Sun May 20 15:37:16 2018 +0200
@@ -32,8 +32,7 @@
     val parents = Theory.parents_of thy;
     val _ =
       export_body thy "parents"
-        let open XML.Encode
-        in list string (map Context.theory_long_name parents) end;
+        (XML.Encode.string (cat_lines (map Context.theory_long_name parents)));
 
 
     (* entities *)