diff --git a/bin/tests/system/conf.sh.in b/bin/tests/system/conf.sh.in
index fc5d264f98..54c339b8f4 100644
--- a/bin/tests/system/conf.sh.in
+++ b/bin/tests/system/conf.sh.in
@@ -114,6 +114,9 @@ SHELL=@SHELL@
 # CURL will be empty if no program was found by configure
 CURL=@CURL@
 
+# GNUTLS_CLI will be empty if no program was found by configure
+GNUTLS_CLI=@GNUTLS_CLI@
+
 # NC will be empty if no program was found by configure
 NC=@NC@
 
diff --git a/bin/tests/system/doth/clean.sh b/bin/tests/system/doth/clean.sh
index b0fcfdf23f..b0915f53aa 100644
--- a/bin/tests/system/doth/clean.sh
+++ b/bin/tests/system/doth/clean.sh
@@ -20,5 +20,6 @@ rm -f ./*/named.memstats
 rm -f ./*/named.run
 rm -f ./*/named.run.prev
 rm -f ./dig.out.*
+rm -f ./example-soa-*.test*
 rm -f ./*/example*.db
 rm -rf ./headers.*
diff --git a/bin/tests/system/doth/example-soa-answer.good b/bin/tests/system/doth/example-soa-answer.good
new file mode 100644
index 0000000000..d462dc684d
Binary files /dev/null and b/bin/tests/system/doth/example-soa-answer.good differ
diff --git a/bin/tests/system/doth/example-soa-request.saved b/bin/tests/system/doth/example-soa-request.saved
new file mode 100644
index 0000000000..d5225b2515
Binary files /dev/null and b/bin/tests/system/doth/example-soa-request.saved differ
diff --git a/bin/tests/system/doth/tests.sh b/bin/tests/system/doth/tests.sh
index a07e9a5849..e9bcb89405 100644
--- a/bin/tests/system/doth/tests.sh
+++ b/bin/tests/system/doth/tests.sh
@@ -582,5 +582,29 @@ if [ -n "$testcurl" ]; then
 	status=$((status + ret))
 fi
 
+# check whether we can use gnutls-cli for sending test queries.
+if [ -x "${GNUTLS_CLI}" ] ; then
+	GNUTLS_CLI_CHECK="$(${GNUTLS_CLI} --logfile=/dev/null 2>&1 | grep -i 'illegal option')"
+
+	if [ -n "$GNUTLS_CLI_CHECK" ]; then
+		echo_i "The available version of gnutls-cli does not support the required features"
+	else
+		testgnutls=1
+	fi
+fi
+
+if [ -n "${testgnutls}" ] ; then
+	n=$((n + 1))
+	echo_i "checking sending a DoT query using gnutls-cli ($n)"
+	ret=0
+	# use gnutls-cli to query for 'example/SOA',
+	# use a timeout with a second empty `cat` because EOF in `stdin`
+	# causes gnutls-cli to disconnect without waiting for the answer
+	( cat example-soa-request.saved && timeout 10 cat ) | "${GNUTLS_CLI}" --no-ca-verification --no-ocsp --alpn=dot --logfile=/dev/null --port=${TLSPORT} 10.53.0.1 > example-soa-answer.test$n 2>&1
+	diff example-soa-answer.good example-soa-answer.test$n > /dev/null 2>&1 || ret=1
+	if [ $ret != 0 ]; then echo_i "failed"; fi
+	status=$((status + ret))
+fi
+
 echo_i "exit status: $status"
 [ $status -eq 0 ] || exit 1
diff --git a/configure.ac b/configure.ac
index b525a080d6..580095ef75 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1259,6 +1259,13 @@ AC_CONFIG_FILES([doc/doxygen/doxygen-input-filter],
 AC_PATH_PROG(CURL, curl, curl)
 AC_SUBST(CURL)
 
+#
+# Look for gnutls-cli
+#
+
+AC_PATH_PROG([GNUTLS_CLI], [gnutls-cli], [])
+AC_SUBST(GNUTLS_CLI)
+
 #
 # Look for nc
 #
diff --git a/lib/isc/tls.c b/lib/isc/tls.c
index 2d24481882..35b8a1277e 100644
--- a/lib/isc/tls.c
+++ b/lib/isc/tls.c
@@ -36,6 +36,7 @@
 #include <isc/mutex.h>
 #include <isc/mutexblock.h>
 #include <isc/once.h>
+#include <isc/random.h>
 #include <isc/refcount.h>
 #include <isc/rwlock.h>
 #include <isc/thread.h>
@@ -317,16 +318,16 @@ isc_tlsctx_createserver(const char *keyfile, const char *certfile,
 			goto ssl_error;
 		}
 
-		/* We use a named curve and compressed point conversion form. */
+		/* Use a named curve and uncompressed point conversion form. */
 #if HAVE_EVP_PKEY_GET0_EC_KEY
 		EC_KEY_set_asn1_flag(EVP_PKEY_get0_EC_KEY(pkey),
 				     OPENSSL_EC_NAMED_CURVE);
 		EC_KEY_set_conv_form(EVP_PKEY_get0_EC_KEY(pkey),
-				     POINT_CONVERSION_COMPRESSED);
+				     POINT_CONVERSION_UNCOMPRESSED);
 #else
 		EC_KEY_set_asn1_flag(pkey->pkey.ec, OPENSSL_EC_NAMED_CURVE);
 		EC_KEY_set_conv_form(pkey->pkey.ec,
-				     POINT_CONVERSION_COMPRESSED);
+				     POINT_CONVERSION_UNCOMPRESSED);
 #endif /* HAVE_EVP_PKEY_GET0_EC_KEY */
 
 #if defined(SSL_CTX_set_ecdh_auto)
@@ -389,7 +390,9 @@ isc_tlsctx_createserver(const char *keyfile, const char *certfile,
 		if (cert == NULL) {
 			goto ssl_error;
 		}
-		ASN1_INTEGER_set(X509_get_serialNumber(cert), 1);
+
+		ASN1_INTEGER_set(X509_get_serialNumber(cert),
+				 (long)isc_random32());
 
 #if OPENSSL_VERSION_NUMBER < 0x10101000L
 		X509_gmtime_adj(X509_get_notBefore(cert), 0);