diff --git a/Koha/Old/Checkouts.pm b/Koha/Old/Checkouts.pm
index 5ba2bec6d2..8ee651645f 100644
--- a/Koha/Old/Checkouts.pm
+++ b/Koha/Old/Checkouts.pm
@@ -96,7 +96,10 @@ Anonymize the given I<Koha::Old::Checkouts> resultset.
 sub anonymize {
     my ( $self, $params ) = @_;
 
-    my $anonymous_id = C4::Context->preference('AnonymousPatron') || undef;
+    my $anonymous_id = C4::Context->preference('AnonymousPatron');
+
+    Koha::Exceptions::SysPref::NotSet->throw( syspref => 'AnonymousPatron' )
+        unless $anonymous_id;
 
     return $self->update( { borrowernumber => $anonymous_id }, { no_triggers => 1 } );
 }
diff --git a/Koha/Old/Hold.pm b/Koha/Old/Hold.pm
index 33642b33f6..aa164fcd2a 100644
--- a/Koha/Old/Hold.pm
+++ b/Koha/Old/Hold.pm
@@ -22,6 +22,7 @@ use Modern::Perl;
 use base qw(Koha::Hold);
 
 use C4::Context;
+use Koha::Exceptions::SysPref;
 
 =head1 NAME
 
@@ -44,7 +45,10 @@ Anonymize the given I<Koha::Old::Hold> object.
 sub anonymize {
     my ($self) = @_;
 
-    my $anonymous_id = C4::Context->preference('AnonymousPatron') || undef;
+    my $anonymous_id = C4::Context->preference('AnonymousPatron');
+
+    Koha::Exceptions::SysPref::NotSet->throw( syspref => 'AnonymousPatron' )
+        unless $anonymous_id;
 
     return $self->update( { borrowernumber => $anonymous_id } );
 }
diff --git a/Koha/Old/Holds.pm b/Koha/Old/Holds.pm
index 1a7cb0d5a7..d3aad2ee89 100644
--- a/Koha/Old/Holds.pm
+++ b/Koha/Old/Holds.pm
@@ -78,7 +78,10 @@ Anonymize the given I<Koha::Old::Holds> resultset.
 sub anonymize {
     my ( $self, $params ) = @_;
 
-    my $anonymous_id = C4::Context->preference('AnonymousPatron') || undef;
+    my $anonymous_id = C4::Context->preference('AnonymousPatron');
+
+    Koha::Exceptions::SysPref::NotSet->throw( syspref => 'AnonymousPatron' )
+        unless $anonymous_id;
 
     return $self->update( { borrowernumber => $anonymous_id }, { no_triggers => 1 } );
 }