1 files changed, 1 insertions, 1 deletions
diff --git a/isa/isa.el b/isa/isa.el
index 3f1e6b0f..48418438 100644
--- a/isa/isa.el
+++ b/isa/isa.el
@@ -481,7 +481,7 @@ you will be asked to retract the file or process the remainder of it."
 ;;
 
 (defcustom isa-not-undoable-commands-regexp
-  (proof-ids-to-regexp '("undo" "back"))
+  (proof-ids-to-regexp '("undo"))
   "Regular expression matching commands which are *not* undoable."
   :type 'regexp
   :group 'isabelle-config)