diff --git a/lib/MySQL_Monitor.cpp b/lib/MySQL_Monitor.cpp
index 9c4575d5e..a6fcb3fd7 100644
--- a/lib/MySQL_Monitor.cpp
+++ b/lib/MySQL_Monitor.cpp
@@ -1492,25 +1492,30 @@ __exit_monitor_replication_lag_thread:
 					int j=-1;
 					num_fields = mysql_num_fields(mmsd->result);
 					fields = mysql_fetch_fields(mmsd->result);
-					for(k = 0; k < num_fields; k++) {
-						if (strcmp("Seconds_Behind_Master", fields[k].name)==0) {
-							j=k;
+					if (fields) {
+						for(k = 0; k < num_fields; k++) {
+							if (strcmp("Seconds_Behind_Master", fields[k].name)==0) {
+								j=k;
+							}
 						}
-					}
-					if (j>-1) {
-						MYSQL_ROW row=mysql_fetch_row(mmsd->result);
-						if (row) {
-							repl_lag=-1; // this is old behavior
+						if (j>-1) {
+							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]);
+									repl_lag=atoi(row[j]);
+								}
 							}
 						}
-					}
-					if (repl_lag>=0) {
-						rc=sqlite3_bind_int64(statement, 5, repl_lag); assert(rc==SQLITE_OK);
+						if (repl_lag>=0) {
+							rc=sqlite3_bind_int64(statement, 5, repl_lag); assert(rc==SQLITE_OK);
+						} else {
+							rc=sqlite3_bind_null(statement, 5); assert(rc==SQLITE_OK);
+						}
 					} else {
-						rc=sqlite3_bind_null(statement, 5); assert(rc==SQLITE_OK);
+							proxy_error("mysql_fetch_fields returns NULL, please report a bug\n");
+							rc=sqlite3_bind_null(statement, 5); assert(rc==SQLITE_OK);
 					}
 					mysql_free_result(mmsd->result);
 					mmsd->result=NULL;
diff --git a/lib/MySQL_Protocol.cpp b/lib/MySQL_Protocol.cpp
index c414f66a8..1dfc4d812 100644
--- a/lib/MySQL_Protocol.cpp
+++ b/lib/MySQL_Protocol.cpp
@@ -1713,7 +1713,7 @@ __do_auth:
 				}
 			} else {
 				if (auth_plugin_id == 1) {
-					if (session_type == PROXYSQL_SESSION_MYSQL || session_type == PROXYSQL_SESSION_SQLITE || PROXYSQL_SESSION_ADMIN || PROXYSQL_SESSION_STATS) {
+					if (session_type == PROXYSQL_SESSION_MYSQL || session_type == PROXYSQL_SESSION_SQLITE || session_type == PROXYSQL_SESSION_ADMIN || session_type == PROXYSQL_SESSION_STATS) {
 						ret=proxy_scramble_sha1((char *)pass,(*myds)->myconn->scramble_buff,password+1, reply);
 						if (ret) {
 							if (sha1_pass==NULL) {
@@ -1726,7 +1726,7 @@ __do_auth:
 						}
 					}
 				} else { // mysql_clear_password
-					if (session_type == PROXYSQL_SESSION_MYSQL || session_type == PROXYSQL_SESSION_SQLITE || PROXYSQL_SESSION_ADMIN || PROXYSQL_SESSION_STATS) {
+					if (session_type == PROXYSQL_SESSION_MYSQL || session_type == PROXYSQL_SESSION_SQLITE || session_type == PROXYSQL_SESSION_ADMIN || session_type == PROXYSQL_SESSION_STATS) {
 /*
 						char sha1_2[SHA_DIGEST_LENGTH+1];
 						sha1_2[SHA_DIGEST_LENGTH]='\0';
diff --git a/lib/ProxySQL_HTTP_Server.cpp b/lib/ProxySQL_HTTP_Server.cpp
index d0f1637da..5b05bf853 100644
--- a/lib/ProxySQL_HTTP_Server.cpp
+++ b/lib/ProxySQL_HTTP_Server.cpp
@@ -125,7 +125,7 @@ static char *generate_home() {
 	html.append("<b>Uptime = </b>");
 	{
 		unsigned long long t1=monotonic_time();
-		char buf1[30];
+		char buf1[50];
 		unsigned long long uptime = (t1-GloVars.global.start_time)/1000/1000;
 		unsigned long long days = uptime / 86400;
 		unsigned long long hours = (uptime - days*86400)/3600;
diff --git a/lib/mysql_connection.cpp b/lib/mysql_connection.cpp
index 318ba4a9c..fbdb26296 100644
--- a/lib/mysql_connection.cpp
+++ b/lib/mysql_connection.cpp
@@ -1641,7 +1641,7 @@ bool MySQL_Connection::MultiplexDisabled() {
 bool MySQL_Connection::IsKeepMultiplexEnabledVariables(char *query_digest_text) {
 	if (query_digest_text==NULL) return true;
 
-	char *query_digest_text_filter_select;
+	char *query_digest_text_filter_select = NULL;
 	unsigned long query_digest_text_len=strlen(query_digest_text);
 	if (strncasecmp(query_digest_text,"SELECT ",strlen("SELECT "))==0){
 		query_digest_text_filter_select=(char*)malloc(query_digest_text_len-7+1);
diff --git a/lib/mysql_data_stream.cpp b/lib/mysql_data_stream.cpp
index 4f3ee0bb1..95c889e48 100644
--- a/lib/mysql_data_stream.cpp
+++ b/lib/mysql_data_stream.cpp
@@ -871,7 +871,7 @@ int MySQL_Data_Stream::buffer2array() {
 	}
 	if ((queueIN.pkt.size>0) && (queueIN.pkt.size==queueIN.partial) ) {
 		if (myconn->get_status_compression()==true) {
-			Bytef *dest;
+			Bytef *dest = NULL;
 			uLongf destLen;
 			proxy_debug(PROXY_DEBUG_PKT_ARRAY, 5, "Copied the whole compressed packet\n");
 			unsigned int progress=0;