diff --git a/bin/pt-table-checksum b/bin/pt-table-checksum
index 0e286430..54eabda1 100755
--- a/bin/pt-table-checksum
+++ b/bin/pt-table-checksum
@@ -9722,12 +9722,20 @@ sub main {
              for my $slave (@$slave_lag_cxns) {
                  my $found=0;
                  for my $slave_to_skip (@$slaves_to_skip) {
-                     if ($slave->{dsn}->{h} eq $slave_to_skip->{h} && $slave->{dsn}->{P} eq $slave_to_skip->{P}) {
+                     my $h_eq_h = $slave->{dsn}->{h} eq $slave_to_skip->{h};
+                     my $p_eq_p;
+                     if (defined($slave->{dsn}->{P}) || defined($slave_to_skip->{P})) {
+                       $p_eq_p = $slave->{dsn}->{P} eq $slave_to_skip->{P};
+                     } else {
+                       PTDEBUG && _d("Both port DSNs are undefined, setting p_eq_p to true");
+                       $p_eq_p = 1;
+                     }
+                     if ($h_eq_h && $p_eq_p) {
                          $found=1;
                      }
                  }
                  if ($found) {
-                    printf("Skipping slave %s -> %s:%s\n", $slave->name(), $slave->{dsn}->{h}, $slave->{dsn}->{P});
+                    printf("Skipping slave %s\n", $slave->name());
                  } else {
                     push @$filtered_slaves, $slave;
                 }