diff --git a/plugins/helper/database/connutil/cassandra.go b/plugins/helper/database/connutil/cassandra.go
index 27fb25195..958bef201 100644
--- a/plugins/helper/database/connutil/cassandra.go
+++ b/plugins/helper/database/connutil/cassandra.go
@@ -48,6 +48,9 @@ func (c *CassandraConnectionProducer) Initialize(conf map[string]interface{}, ve
 	}
 	c.Initialized = true
 
+	if c.ConnectTimeoutRaw == nil {
+		c.ConnectTimeoutRaw = "0s"
+	}
 	c.connectTimeout, err = parseutil.ParseDurationSecond(c.ConnectTimeoutRaw)
 	if err != nil {
 		return fmt.Errorf("invalid connect_timeout: %s", err)
diff --git a/plugins/helper/database/connutil/sql.go b/plugins/helper/database/connutil/sql.go
index 4a6368560..5067e10d7 100644
--- a/plugins/helper/database/connutil/sql.go
+++ b/plugins/helper/database/connutil/sql.go
@@ -48,7 +48,7 @@ func (c *SQLConnectionProducer) Initialize(conf map[string]interface{}, verifyCo
 	if c.MaxIdleConnections > c.MaxOpenConnections {
 		c.MaxIdleConnections = c.MaxOpenConnections
 	}
-	if c.MaxConnectionLifetimeRaw == "" {
+	if c.MaxConnectionLifetimeRaw == nil {
 		c.MaxConnectionLifetimeRaw = "0s"
 	}