diff --git a/t/pt-heartbeat/pxc.t b/t/pt-heartbeat/pxc.t
index 0f6cc7b7..3b0f2424 100644
--- a/t/pt-heartbeat/pxc.t
+++ b/t/pt-heartbeat/pxc.t
@@ -132,7 +132,7 @@ is_deeply(
       12347 => $same_data,
    },
    "Sanity check: No slave data (relay log or master pos) is stored"
-);
+) or diag(Dumper($rows));
 
 $output = output(sub{
       pt_heartbeat::main($node1_dsn, qw(-D test --check)),