diff --git a/lib/Autom4te/C4che.pm b/lib/Autom4te/C4che.pm
index 523f15bf..029138d1 100644
--- a/lib/Autom4te/C4che.pm
+++ b/lib/Autom4te/C4che.pm
@@ -155,13 +155,16 @@ Serialize all the current requests.
 sub marshall ($)
 {
   my ($caller) = @_;
-  my $res = '';
 
   my $marshall = Data::Dumper->new ([\@request], [qw (*request)]);
-  $marshall->Indent(2)->Terse(0)->Sortkeys(1);
-  $res = $marshall->Dump . "\n";
+  $marshall->Indent(2)->Terse(0);
 
-  return $res;
+  # The Sortkeys method was added in Data::Dumper 2.12_01, so it is
+  # available in 5.8.x and 5.6.2 but not in 5.6.1 or earlier.
+  # Ignore failure of method lookup.
+  eval { $marshall->Sortkeys(1); };
+
+  return $marshall->Dump . "\n";
 }
 
 
diff --git a/lib/Autom4te/Request.pm b/lib/Autom4te/Request.pm
index 53f9ad7a..f4ede8df 100644
--- a/lib/Autom4te/Request.pm
+++ b/lib/Autom4te/Request.pm
@@ -59,14 +59,17 @@ struct
 sub marshall($)
 {
   my ($caller) = @_;
-  my $res = '';
 
   # CALLER is an object: instance method.
   my $marshall = Data::Dumper->new ([$caller]);
-  $marshall->Indent(2)->Terse(0)->Sortkeys(1);
-  $res = $marshall->Dump . "\n";
+  $marshall->Indent(2)->Terse(0);
 
-  return $res;
+  # The Sortkeys method was added in Data::Dumper 2.12_01, so it is
+  # available in 5.8.x and 5.6.2 but not in 5.6.1 or earlier.
+  # Ignore failure of method lookup.
+  eval { $marshall->Sortkeys(1); };
+
+  return $marshall->Dump . "\n";
 }