1 files changed, 2 insertions, 2 deletions
diff --git a/isa/isa.el b/isa/isa.el
index 1bdb7a91..acbb2b75 100644
--- a/isa/isa.el
+++ b/isa/isa.el
@@ -637,8 +637,8 @@ you will be asked to retract the file or process the remainder of it."
       ;; fontification for tokens themselves  (FIXME: broken)
       '(("\\\\<[A-Za-z][A-Za-z0-9_']*>" (0 font-lock-type-face)))
       proof-xsym-activate-command
-      "print_mode := (!print_mode union [\"xsymbols\",\"symbols\"])"
+      "print_mode := ([\"xsymbols\",\"symbols\"] @ ! print_mode)"
       proof-xsym-deactivate-command
-      "print_mode := filter_out (fn x=>(rev (explode \"symbols\") prefix rev (explode x))) (!print_mode)")
+      "print_mode := (! print_mode \\\\ [\"xsymbols\",\"symbols\"])")
 
 (provide 'isa)