diff --git a/IO/Storable/storable.pd b/IO/Storable/storable.pd
index da2ec0e80..9acbbee8d 100644
--- a/IO/Storable/storable.pd
+++ b/IO/Storable/storable.pd
@@ -290,8 +290,7 @@ sub STORABLE_thaw {
 #  return if $cloning;
   my $class = ref $pdl;
   if (defined $hashref) {
-    croak "serial data with hashref!" unless !defined $serial ||
-      $serial eq "";
+    croak "serial data with hashref!" unless ($serial//'') eq "";
     @$pdl{keys %$hashref} = values %$hashref;
   } else {
     # all the magic is happening in pdlunpack