--- loncom/homework/lonhomework.pm	2016/05/13 22:48:09	1.361
+++ loncom/homework/lonhomework.pm	2016/05/30 02:45:32	1.362
@@ -1,7 +1,7 @@
 # The LearningOnline Network with CAPA
 # The LON-CAPA Homework handler
 #
-# $Id: lonhomework.pm,v 1.361 2016/05/13 22:48:09 raeburn Exp $
+# $Id: lonhomework.pm,v 1.362 2016/05/30 02:45:32 raeburn Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -561,15 +561,16 @@ sub check_access {
     if ($status eq 'CAN_ANSWER' || $status eq 'CANNOT_ANSWER') {
 	my @interval=&Apache::lonnet::EXT("resource.$id.interval",$symb);
 	&Apache::lonxml::debug("looking for interval @interval");
-	if ($interval[0]) {
+	if ($interval[0]=~ /^\d+/) {
 	    my $first_access=&Apache::lonnet::get_first_access($interval[1],$symb);
 	    &Apache::lonxml::debug("looking for accesstime $first_access");
 	    if (!$first_access) {
 		$status='NOT_YET_VIEWED';
 		my $due_date = &due_date($id,$symb);
 		my $seconds_left = $due_date - time;
-		if ($seconds_left > $interval[0] || $due_date eq '') {
-		    $seconds_left = $interval[0];
+		my ($timelimit) = ($interval[0] =~ /^(\d+)/);
+		if ($seconds_left > $timelimit || $due_date eq '') {
+		    $seconds_left = $timelimit;
 		}
 		$datemsg=&seconds_to_human_length($seconds_left);
 	    }
@@ -604,7 +605,8 @@ sub due_date {
 	my $first_access=&Apache::lonnet::get_first_access($interval[1],$symb);
 	&Apache::lonxml::debug("looking for first_access $first_access ($interval[1])");
 	if (defined($first_access)) {
-	    my $interval = $first_access+$interval[0];
+	    my ($timelimit) = ($interval[0] =~ /^(\d+)/);
+	    my $interval = $first_access+$timelimit;
 	    $date = (!$due_date || $interval < $due_date) ? $interval
                                                           : $due_date;
 	} else {