diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index dc8f910ea46..c94fe584177 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -201,6 +201,10 @@ static bool check_cluster_name(char **newval, void **extra, GucSource source);
 static const char *show_unix_socket_permissions(void);
 static const char *show_log_file_mode(void);
 static const char *show_data_directory_mode(void);
+static bool check_ssl_min_protocol_version(int *newval, void **extra,
+										   GucSource source);
+static bool check_ssl_max_protocol_version(int *newval, void **extra,
+										   GucSource source);
 static bool check_recovery_target_timeline(char **newval, void **extra, GucSource source);
 static void assign_recovery_target_timeline(const char *newval, void *extra);
 static bool check_recovery_target(char **newval, void **extra, GucSource source);
@@ -4522,7 +4526,7 @@ static struct config_enum ConfigureNamesEnum[] =
 		&ssl_min_protocol_version,
 		PG_TLS1_VERSION,
 		ssl_protocol_versions_info + 1, /* don't allow PG_TLS_ANY */
-		NULL, NULL, NULL
+		check_ssl_min_protocol_version, NULL, NULL
 	},
 
 	{
@@ -4534,7 +4538,7 @@ static struct config_enum ConfigureNamesEnum[] =
 		&ssl_max_protocol_version,
 		PG_TLS_ANY,
 		ssl_protocol_versions_info,
-		NULL, NULL, NULL
+		check_ssl_max_protocol_version, NULL, NULL
 	},
 
 	/* End-of-list marker */
@@ -11462,6 +11466,49 @@ show_data_directory_mode(void)
 	return buf;
 }
 
+static bool
+check_ssl_min_protocol_version(int *newval, void **extra, GucSource source)
+{
+	int			new_ssl_min_protocol_version = *newval;
+
+	/* PG_TLS_ANY is not supported for the minimum bound */
+	Assert(new_ssl_min_protocol_version > PG_TLS_ANY);
+
+	if (ssl_max_protocol_version &&
+		new_ssl_min_protocol_version > ssl_max_protocol_version)
+	{
+		GUC_check_errhint("\"%s\" cannot be higher than \"%s\".",
+						  "ssl_min_protocol_version",
+						  "ssl_max_protocol_version");
+		GUC_check_errcode(ERRCODE_INVALID_PARAMETER_VALUE);
+		return false;
+	}
+
+	return true;
+}
+
+static bool
+check_ssl_max_protocol_version(int *newval, void **extra, GucSource source)
+{
+	int			new_ssl_max_protocol_version = *newval;
+
+	/* if PG_TLS_ANY, there is no need to check the bounds */
+	if (new_ssl_max_protocol_version == PG_TLS_ANY)
+		return true;
+
+	if (ssl_min_protocol_version &&
+		ssl_min_protocol_version > new_ssl_max_protocol_version)
+	{
+		GUC_check_errhint("\"%s\" cannot be lower than \"%s\".",
+						  "ssl_max_protocol_version",
+						  "ssl_min_protocol_version");
+		GUC_check_errcode(ERRCODE_INVALID_PARAMETER_VALUE);
+		return false;
+	}
+
+	return true;
+}
+
 static bool
 check_recovery_target_timeline(char **newval, void **extra, GucSource source)
 {
diff --git a/src/test/ssl/t/001_ssltests.pl b/src/test/ssl/t/001_ssltests.pl
index 67a3a28db6a..66278381bd2 100644
--- a/src/test/ssl/t/001_ssltests.pl
+++ b/src/test/ssl/t/001_ssltests.pl
@@ -13,7 +13,7 @@ use SSLServer;
 
 if ($ENV{with_openssl} eq 'yes')
 {
-	plan tests => 75;
+	plan tests => 77;
 }
 else
 {
@@ -87,6 +87,24 @@ command_ok(
 	'restart succeeds with password-protected key file');
 $node->_update_pid(1);
 
+# Test compatibility of SSL protocols.
+# TLSv1.1 is lower than TLSv1.2, so it won't work.
+$node->append_conf(
+	'postgresql.conf',
+	qq{ssl_min_protocol_version='TLSv1.2'
+ssl_max_protocol_version='TLSv1.1'});
+command_fails(
+	[ 'pg_ctl', '-D', $node->data_dir, '-l', $node->logfile, 'restart' ],
+	'restart fails with incorrect SSL protocol bounds');
+# Go back to the defaults, this works.
+$node->append_conf(
+	'postgresql.conf',
+	qq{ssl_min_protocol_version='TLSv1'
+ssl_max_protocol_version=''});
+command_ok(
+	[ 'pg_ctl', '-D', $node->data_dir, '-l', $node->logfile, 'restart' ],
+	'restart succeeds with correct SSL protocol bounds');
+
 ### Run client-side tests.
 ###
 ### Test that libpq accepts/rejects the connection correctly, depending
diff --git a/src/test/ssl/t/SSLServer.pm b/src/test/ssl/t/SSLServer.pm
index d25c38dbbc7..228cddf3a2c 100644
--- a/src/test/ssl/t/SSLServer.pm
+++ b/src/test/ssl/t/SSLServer.pm
@@ -128,7 +128,7 @@ sub configure_test_server_for_ssl
 	print $conf "log_statement=all\n";
 
 	# enable SSL and set up server key
-	print $conf "include 'sslconfig.conf'";
+	print $conf "include 'sslconfig.conf'\n";
 
 	close $conf;