diff --git a/bin/tests/system/tcp/tests.sh b/bin/tests/system/tcp/tests.sh
index 6074427c6f..4faadaa1cb 100644
--- a/bin/tests/system/tcp/tests.sh
+++ b/bin/tests/system/tcp/tests.sh
@@ -183,9 +183,15 @@ grep "status: NXDOMAIN" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
 status=$((status + ret))
 
+####################################################
+# NOTE: The next test resets the debug level to 1. #
+####################################################
+
 n=$((n + 1))
 echo_i "checking that BIND 9 doesn't crash on long TCP messages ($n)"
 ret=0
+# Avoid logging useless information.
+rndccmd 10.53.0.1 trace 1 || ret=1
 { $PERL ../packet.pl -a "10.53.0.1" -p "${PORT}" -t tcp -r 300000 1996-alloc_dnsbuf-crash-test.pkt || ret=1 ; } | cat_i
 dig_with_opts +tcp @10.53.0.1 txt.example > dig.out.test$n || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi