diff --git a/consumergroup.go b/consumergroup.go
index 92c622c7..00380ce9 100644
--- a/consumergroup.go
+++ b/consumergroup.go
@@ -8,6 +8,8 @@ import (
 	"fmt"
 	"io"
 	"math"
+	"net"
+	"strconv"
 	"strings"
 	"sync"
 	"time"
@@ -861,7 +863,7 @@ func (cg *ConsumerGroup) coordinator() (coordinator, error) {
 		return nil, err
 	}
 
-	address := fmt.Sprintf("%v:%v", out.Coordinator.Host, out.Coordinator.Port)
+	address := net.JoinHostPort(out.Coordinator.Host, strconv.Itoa(int(out.Coordinator.Port)))
 	return cg.config.connect(cg.config.Dialer, address)
 }
 
diff --git a/initproducerid_test.go b/initproducerid_test.go
index 5f1bb59a..480175f4 100644
--- a/initproducerid_test.go
+++ b/initproducerid_test.go
@@ -3,7 +3,8 @@ package kafka
 import (
 	"context"
 	"errors"
-	"fmt"
+	"net"
+	"strconv"
 	"testing"
 	"time"
 
@@ -31,7 +32,7 @@ func TestClientInitProducerId(t *testing.T) {
 	}
 
 	// Now establish a connection with the transaction coordinator
-	transactionCoordinator := TCP(fmt.Sprintf("%s:%d", respc.Coordinator.Host, respc.Coordinator.Port))
+	transactionCoordinator := TCP(net.JoinHostPort(respc.Coordinator.Host, strconv.Itoa(int(respc.Coordinator.Port))))
 	client, shutdown = newClient(transactionCoordinator)
 	defer shutdown()