diff --git a/lib/WeBWorK/ContentGenerator/GatewayQuiz.pm b/lib/WeBWorK/ContentGenerator/GatewayQuiz.pm
index 690905d779..bf505320db 100644
--- a/lib/WeBWorK/ContentGenerator/GatewayQuiz.pm
+++ b/lib/WeBWorK/ContentGenerator/GatewayQuiz.pm
@@ -1019,7 +1019,9 @@ sub pre_header_initialize {
 	    );
 	foreach my $key (keys %$formFields) {
 	    if ($key =~ /AnSwEr/) {
-		$formFields->{$key} = $scrubber->scrub($formFields->{$key});
+		$formFields->{$key} = $scrubber->scrub(		
+			(defined $formFields->{$key})? $formFields->{key}:'' # using // would be more elegant but breaks perl 5.8.x
+		);
 		### HTML::scrubber is a little too enthusiastic about
 		### removing > and < so we have to add them back in otherwise
 		### they confuse pg
diff --git a/lib/WeBWorK/ContentGenerator/Instructor/ProblemGrader.pm b/lib/WeBWorK/ContentGenerator/Instructor/ProblemGrader.pm
index 4db7a37545..e849ce9b0a 100644
--- a/lib/WeBWorK/ContentGenerator/Instructor/ProblemGrader.pm
+++ b/lib/WeBWorK/ContentGenerator/Instructor/ProblemGrader.pm
@@ -141,7 +141,7 @@ sub initialize {
 			comment => 0
 			);
 		    
-		    my $comment = $scrubber->scrub($r->param("$userID.comment"));
+		    my $comment = $scrubber->scrub( ( defined $r->param("$userID.comment") )?$r->param("$userID.comment"):'' );
 		    my $userPastAnswerID = $db->latestProblemPastAnswer($courseName, $userID, $setID, $problemID); 
 		    
 		    if ($userPastAnswerID) {
diff --git a/lib/WeBWorK/ContentGenerator/Problem.pm b/lib/WeBWorK/ContentGenerator/Problem.pm
index 38b20ce3cb..c5dfa4c2ea 100644
--- a/lib/WeBWorK/ContentGenerator/Problem.pm
+++ b/lib/WeBWorK/ContentGenerator/Problem.pm
@@ -732,7 +732,9 @@ sub pre_header_initialize {
 	    );
 	foreach my $key (keys %$formFields) {
 	    if ($key =~ /AnSwEr/) {
-		$formFields->{$key} = $scrubber->scrub($formFields->{$key});
+		$formFields->{$key} = $scrubber->scrub(		
+			(defined $formFields->{$key})? $formFields->{key}:'' # using // would be more elegant but breaks perl 5.8.x
+		);
 		### HTML::scrubber is a little too enthusiastic about
 		### removing > and < so we have to add them back in otherwise
 		### they confuse pg