diff --git a/lib/Value/AnswerChecker.pm b/lib/Value/AnswerChecker.pm
index 976e45c37c..f5ddb665ff 100644
--- a/lib/Value/AnswerChecker.pm
+++ b/lib/Value/AnswerChecker.pm
@@ -1731,6 +1731,7 @@ sub cmp_postfilter {
   return $ans if ($ans->{bypass_equivalence_test});
   my $context = $self->context;
   Parser::Context->current(undef,$context);
+  my $flags = Value::contextSet($context,$self->cmp_contextFlags($ans)); # save old context flags
   $ans->{prev_formula} = Parser::Formula($ans->{prev_ans});
   if (defined($ans->{prev_formula}) && defined($ans->{student_formula})) {
     my $prev = eval {$self->promote($ans->{prev_formula})->inherit($self)}; # inherit limits, etc.
@@ -1744,6 +1745,7 @@ sub cmp_postfilter {
 	and $ans->{prev_ans} ne $ans->{original_student_ans}) # but not identical
       {$ans->{ans_message} = "This answer is equivalent to the one you just submitted."}
   }
+  Value::contextSet($context,%{$flags});            # restore context values
   return $ans;
 }
 
diff --git a/lib/Value/Real.pm b/lib/Value/Real.pm
index c7cb654719..5817dd84ed 100644
--- a/lib/Value/Real.pm
+++ b/lib/Value/Real.pm
@@ -195,7 +195,7 @@ sub atan2 {
 ##################################################
 
 sub string {
-  my $self = shift; my $equation = shift; my $prec = shift;
+  my $self = shift; my $equation = shift; shift; shift; my $prec = shift;
   my $n = $self->{data}[0];
   my $format = $self->getFlag("format",$equation->{format} ||
 			        ($equation->{context} || $self->context)->{format}{number});
diff --git a/lib/Value/Union.pm b/lib/Value/Union.pm
index 7dbee1f427..d9bdfc1ad6 100644
--- a/lib/Value/Union.pm
+++ b/lib/Value/Union.pm
@@ -335,7 +335,7 @@ sub pdot {
 }
 
 sub string {
-  my $self = shift; my $equation = shift; shift; shift; my $prec = shift//0;
+  my $self = shift; my $equation = shift; shift; shift; my $prec = shift;
   my $op = ($equation->{context} || $self->context)->{operators}{'U'};
   my @intervals = ();
   foreach my $x (@{$self->data}) {
@@ -343,17 +343,17 @@ sub string {
     push(@intervals,$x->string($equation))
   }
   my $string = join($op->{string} || ' U ',@intervals);
-  $string = '('.$string.')' if $prec > ($op->{precedence} || 1.5);
+  $string = '('.$string.')' if defined($prec) && $prec > ($op->{precedence} || 1.5);
   return $string;
 }
 
 sub TeX {
-  my $self = shift; my $equation = shift; shift; shift; my $prec = shift//0; #FIXME find out about precedece
+  my $self = shift; my $equation = shift; shift; shift; my $prec = shift;
   my $op = ($equation->{context} || $self->context)->{operators}{'U'};
   my @intervals = ();
   foreach my $x (@{$self->data}) {push(@intervals,$x->TeX($equation))}
   my $TeX = join($op->{TeX} || $op->{string} || ' U ',@intervals);
-  $TeX = '\left('.$TeX.'\right)' if $prec > ($op->{precedence} || 1.5);
+  $TeX = '\left('.$TeX.'\right)' if defined($prec) && $prec > ($op->{precedence} || 1.5);
   return $TeX;
 }
 
diff --git a/macros/contextFraction.pl b/macros/contextFraction.pl
index bdb4b59df4..2c5585a93a 100644
--- a/macros/contextFraction.pl
+++ b/macros/contextFraction.pl
@@ -892,7 +892,7 @@ sub isReduced {
 #
 
 sub string {
-  my $self = shift; my $equation = shift; my $prec = shift;
+  my $self = shift; my $equation = shift; shift; shift; my $prec = shift;
   my ($a,$b) = @{$self->{data}}; my $n = "";
   return "$a" if $b == 1;
   if ($self->getFlagWithAlias("showMixedNumbers","showProperFractions") && CORE::abs($a) > $b)
@@ -903,7 +903,7 @@ sub string {
 }
 
 sub TeX {
-  my $self = shift; my $equation = shift; my $prec = shift;
+  my $self = shift; my $equation = shift; shift; shift; my $prec = shift;
   my ($a,$b) = @{$self->{data}}; my $n = "";
   return "$a" if $b == 1;
   if ($self->getFlagWithAlias("showMixedNumbers","showProperFractions") && CORE::abs($a) > $b)