From 27662c80cebb51689513c6077705ab33555cc1d6 Mon Sep 17 00:00:00 2001
From: David Aspinall
Date: Wed, 6 Oct 1999 11:33:18 +0000
Subject: Fix for state-preserving-p

---
 isa/isa.el | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/isa/isa.el b/isa/isa.el
index 9482e3dc..c4f58f25 100644
--- a/isa/isa.el
+++ b/isa/isa.el
@@ -546,7 +546,7 @@ Resulting output from Isabelle will be parsed by Proof General."
 
 (defun isa-state-preserving-p (cmd)
   "Non-nil if command preserves the proofstate."
-  (proof-string-match isa-not-undoable-commands-regexp cmd))
+  (not (proof-string-match isa-not-undoable-commands-regexp cmd)))
 
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