--- loncom/homework/default_homework.lcpm	2008/11/26 18:11:52	1.142
+++ loncom/homework/default_homework.lcpm	2009/02/06 10:43:48	1.143
@@ -1,7 +1,7 @@
 # The LearningOnline Network with CAPA 
 # used by lonxml::xmlparse() as input variable $safeinit to Apache::run::run()
 #
-# $Id: default_homework.lcpm,v 1.142 2008/11/26 18:11:52 raeburn Exp $
+# $Id: default_homework.lcpm,v 1.143 2009/02/06 10:43:48 riegler Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -220,7 +220,7 @@ sub caparesponse_check {
     if (($type eq '9') || ($type eq '8')) {
         if ($response=~/\=/) {
             return ('BAD_FORMULA','Please submit just an expression, not an equation.');
-        } elsif ($response =~ /\,/) {
+        } elsif ($response =~ /\,/ and $response !~ /^\s*\{.*\}\s*$/) {
             return ('BAD_FORMULA');
         }
     }