diff --git a/include/MySQL_HostGroups_Manager.h b/include/MySQL_HostGroups_Manager.h
index eaa71a293c..995e340518 100644
--- a/include/MySQL_HostGroups_Manager.h
+++ b/include/MySQL_HostGroups_Manager.h
@@ -291,6 +291,7 @@ class MyHGC {	// MySQL Host Group Container
 		char * ignore_session_variables_text; // this is the original version (text format) of ignore_session_variables
 		uint32_t max_num_online_servers;
 		uint32_t throttle_connections_per_sec;
+		int32_t monitor_slave_lag_when_null;
 		int8_t autocommit;
 		int8_t free_connections_pct;
 		int8_t handle_warnings;
@@ -310,6 +311,10 @@ class MyHGC {	// MySQL Host Group Container
 	bool handle_warnings_enabled() const {
 		return attributes.configured == true && attributes.handle_warnings != -1 ? attributes.handle_warnings : mysql_thread___handle_warnings;
 	}
+	inline
+	int32_t get_monitor_slave_lag_when_null() const {
+		return attributes.configured == true && attributes.monitor_slave_lag_when_null != -1 ? attributes.monitor_slave_lag_when_null : mysql_thread___monitor_slave_lag_when_null;
+	}
 	MyHGC(int);
 	~MyHGC();
 	MySrvC *get_random_MySrvC(char * gtid_uuid, uint64_t gtid_trxid, int max_lag_ms, MySQL_Session *sess);
diff --git a/lib/MyHGC.cpp b/lib/MyHGC.cpp
index 9a2a8a0629..9602f156a4 100644
--- a/lib/MyHGC.cpp
+++ b/lib/MyHGC.cpp
@@ -33,6 +33,7 @@ void MyHGC::reset_attributes() {
 	attributes.autocommit = -1;
 	attributes.free_connections_pct = 10;
 	attributes.handle_warnings = -1;
+	attributes.monitor_slave_lag_when_null = -1;
 	attributes.multiplex = true;
 	attributes.connection_warming = false;
 	free(attributes.init_connect);
diff --git a/lib/MySQL_HostGroups_Manager.cpp b/lib/MySQL_HostGroups_Manager.cpp
index 705a06515a..d380c3b29a 100644
--- a/lib/MySQL_HostGroups_Manager.cpp
+++ b/lib/MySQL_HostGroups_Manager.cpp
@@ -2686,8 +2686,13 @@ void MySQL_HostGroups_Manager::add(MySrvC *mysrvc, unsigned int _hid) {
 }
 
 void MySQL_HostGroups_Manager::replication_lag_action_inner(MyHGC *myhgc, const char *address, unsigned int port, int current_replication_lag) {
-	int j;
-	for (j=0; j<(int)myhgc->mysrvs->cnt(); j++) {
+	
+	if (current_replication_lag == -1) {
+		current_replication_lag = myhgc->get_monitor_slave_lag_when_null();
+		proxy_error("Replication lag on server %s:%d is NULL, using value %d\n", address, port, current_replication_lag);
+	}
+
+	for (int j=0; j<(int)myhgc->mysrvs->cnt(); j++) {
 		MySrvC *mysrvc=(MySrvC *)myhgc->mysrvs->servers->index(j);
 		if (strcmp(mysrvc->address,address)==0 && mysrvc->port==port) {
 			mysrvc->cur_replication_lag = current_replication_lag;
@@ -6219,8 +6224,13 @@ void init_myhgc_hostgroup_settings(const char* hostgroup_settings, MyHGC* myhgc)
 			nlohmann::json j = nlohmann::json::parse(hostgroup_settings);
 
 			const auto handle_warnings_check = [](int8_t handle_warnings) -> bool { return handle_warnings == 0 || handle_warnings == 1; };
-			int8_t handle_warnings = j_get_srv_default_int_val<int8_t>(j, hid, "handle_warnings", handle_warnings_check);
+			const int8_t handle_warnings = j_get_srv_default_int_val<int8_t>(j, hid, "handle_warnings", handle_warnings_check);
 			myhgc->attributes.handle_warnings = handle_warnings;
+
+			const auto monitor_slave_lag_when_null_check = [](int32_t monitor_slave_lag_when_null) -> bool 
+				{ return (monitor_slave_lag_when_null >= 0 && monitor_slave_lag_when_null <= 604800); };
+			const int32_t monitor_slave_lag_when_null = j_get_srv_default_int_val<int32_t>(j, hid, "monitor_slave_lag_when_null", monitor_slave_lag_when_null_check);
+			myhgc->attributes.monitor_slave_lag_when_null = monitor_slave_lag_when_null;
 		}
 		catch (const json::exception& e) {
 			proxy_error(
diff --git a/lib/MySQL_Monitor.cpp b/lib/MySQL_Monitor.cpp
index a943f10a98..1034129653 100644
--- a/lib/MySQL_Monitor.cpp
+++ b/lib/MySQL_Monitor.cpp
@@ -2792,11 +2792,9 @@ void * monitor_replication_lag_thread(void *arg) {
 							MYSQL_ROW row=mysql_fetch_row(mmsd->result);
 							if (row) {
 								repl_lag=-1; // this is old behavior
-							repl_lag=mysql_thread___monitor_slave_lag_when_null; // new behavior, see 669
 								if (row[j]) { // if Seconds_Behind_Master is not NULL
 									repl_lag=atoi(row[j]);
 								} else {
-									proxy_error("Replication lag on server %s:%d is NULL, using the value %d (mysql-monitor_slave_lag_when_null)\n", mmsd->hostname, mmsd->port, mysql_thread___monitor_slave_lag_when_null);
 									MyHGM->p_update_mysql_error_counter(p_mysql_error_type::proxysql, mmsd->hostgroup_id, mmsd->hostname, mmsd->port, ER_PROXYSQL_SRV_NULL_REPLICATION_LAG);
 								}
 							}
@@ -7820,11 +7818,9 @@ bool MySQL_Monitor::monitor_replication_lag_process_ready_tasks(const std::vecto
 					MYSQL_ROW row = mysql_fetch_row(mmsd->result);
 					if (row) {
 						repl_lag = -1; // this is old behavior
-						repl_lag = mysql_thread___monitor_slave_lag_when_null; // new behavior, see 669
 						if (row[j]) { // if Seconds_Behind_Master is not NULL
 							repl_lag = atoi(row[j]);
 						} else {
-							proxy_error("Replication lag on server %s:%d is NULL, using the value %d (mysql-monitor_slave_lag_when_null)\n", mmsd->hostname, mmsd->port, mysql_thread___monitor_slave_lag_when_null);
 							MyHGM->p_update_mysql_error_counter(p_mysql_error_type::proxysql, mmsd->hostgroup_id, mmsd->hostname, mmsd->port, ER_PROXYSQL_SRV_NULL_REPLICATION_LAG);
 						}
 					}