diff --git a/yatex.el b/yatex.el
index 7c4d6ba..10ba21f 100644
--- a/yatex.el
+++ b/yatex.el
@@ -2,7 +2,7 @@
 ;;; Yet Another tex-mode for emacs - //�쒹//
 ;;; yatex.el rev. 1.74.3
 ;;; (c)1991-2010 by HIROSE Yuuji.[yuuji@yatex.org]
-;;; Last modified Thu May 27 10:09:18 2010 on firestorm
+;;; Last modified Thu May 27 13:45:10 2010 on firestorm
 ;;; $Id$
 ;;; The latest version of this software is always available at;
 ;;; http://www.yatex.org/
@@ -2471,7 +2471,8 @@
 		    (if (match-beginning 2)
 			(setq nest (1+ nest))
 		      (setq nest (1- nest)))
-		    (if (< nest 0) (throw 'open t)))))))
+		    (if (< nest 0)
+			(throw 'open (cons env (match-beginning 0)))))))))
      ((listp env)
       (setq p
 	    (or (YaTeX-in-environment-p (car env))
@@ -2485,21 +2486,25 @@
 ENV is given in the form of environment's name or its list.
 This function returns correct result only if ENV is NOT nested."
   (save-excursion
-    (let ((md (match-data)) (p (point)) rc clfound)
+    (let ((md (match-data)) m0 (p (point)) rc clfound)
       (cond
        ((listp env)
 	(or (YaTeX-quick-in-environment-p (car env))
 	    (and (cdr env) (YaTeX-quick-in-environment-p (cdr env)))))
        (t
-	(if (YaTeX-search-active-backward
-	     (YaTeX-replace-format-args YaTeX-struct-begin env "" "")
-	     YaTeX-comment-prefix nil t)
-	    (setq rc (not (YaTeX-search-active-forward
-			   (YaTeX-replace-format-args
-			    YaTeX-struct-end env)
-			   YaTeX-comment-prefix p t nil))))
-	(store-match-data md)
-	rc)))))
+	(unwind-protect
+	    (if (prog1
+		    (YaTeX-search-active-backward
+		     (YaTeX-replace-format-args YaTeX-struct-begin env "" "")
+		     YaTeX-comment-prefix nil t)
+		  (setq m0 (match-beginning 0)))
+		(if (YaTeX-search-active-forward
+		     (YaTeX-replace-format-args
+		      YaTeX-struct-end env)
+		     YaTeX-comment-prefix p t nil)
+		    nil			;if \end{env} found, return nil
+		  (cons env m0)))	;else, return meaningful values
+	  (store-match-data md)))))))
 
 ;; Filling \item
 (defun YaTeX-remove-trailing-comment (start end)