diff --git a/C4/ClassSplitRoutine/LCC.pm b/C4/ClassSplitRoutine/LCC.pm
index 12901ba3e3..a2ee632960 100644
--- a/C4/ClassSplitRoutine/LCC.pm
+++ b/C4/ClassSplitRoutine/LCC.pm
@@ -46,7 +46,7 @@ sub split_callnumber {
     # lccn examples: 'HE8700.7 .P6T44 1983', 'BS2545.E8 H39 1996';
     my @lines = Library::CallNumber::LC->new($cn_item)->components();
     unless ( scalar @lines && defined $lines[0] ) {
-        Koha::Logger->get->debug( sprintf( 'regexp failed to match string: %s', $cn_item ) );
+        Koha::Logger->get->debug( sprintf( 'regexp failed to match string: %s', $cn_item // q{} ) );
         @lines = $cn_item;    # if no match, just use the whole string.
     }
     my $LastPiece = pop @lines;
diff --git a/t/Labels.t b/t/Labels.t
index 1a5d8b53b1..5facaaed78 100755
--- a/t/Labels.t
+++ b/t/Labels.t
@@ -17,11 +17,11 @@
 #
 # for context, see http://bugs.koha-community.org/bugzilla3/show_bug.cgi?id=2691
 
-use strict;
-use warnings;
+use Modern::Perl;
 
 use C4::ClassSplitRoutine::LCC qw( split_callnumber );
-use Test::More tests => 11;
+use Test::More tests => 12;
+use Test::NoWarnings;
 
 BEGIN {
     use_ok( 'C4::Labels::Label', qw( _get_text_fields _check_params _guide_box ) );