diff --git a/client_notification_test.go b/client_notification_test.go
index 28f7987..8e88a8f 100644
--- a/client_notification_test.go
+++ b/client_notification_test.go
@@ -69,6 +69,20 @@ func TestNotificationExpansionIsSinglePassAndNotifyDoesNotBlock(t *testing.T) {
 	}
 }
 
+func TestServerAddressDefaultsPortWithoutBreakingIPv6(t *testing.T) {
+	for input, want := range map[string]string{
+		"server":          "server:64738",
+		"server:64739":    "server:64739",
+		"::1":             "[::1]:64738",
+		"[2001:db8::1]":   "[2001:db8::1]:64738",
+		"[2001:db8::1]:9": "[2001:db8::1]:9",
+	} {
+		if got := serverAddress(input); got != want {
+			t.Errorf("serverAddress(%q) = %q, want %q", input, got, want)
+		}
+	}
+}
+
 func TestPublicServerMessageDoesNotPanic(t *testing.T) {
 	channel := &gumble.Channel{ID: 1, Name: "Current"}
 	b := &Barnard{
diff --git a/main.go b/main.go
index 95a925d..f82139c 100644
--- a/main.go
+++ b/main.go
@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"io"
 	"log"
+	"net"
 	"net/http"
 	"os"
 	"os/exec"
@@ -226,9 +227,7 @@ func main() {
 		os.Exit(0)
 	}
 
-	if !strings.Contains(*server, ":") {
-		*server = (*server + ":64738")
-	}
+	*server = serverAddress(*server)
 
 	// Initialize
 	b := Barnard{
@@ -282,6 +281,14 @@ func main() {
 	handle_error(&b)
 }
 
+// serverAddress adds Mumble's default port without corrupting an IPv6 literal.
+func serverAddress(address string) string {
+	if _, port, err := net.SplitHostPort(address); err == nil && port != "" {
+		return address
+	}
+	return net.JoinHostPort(strings.Trim(address, "[]"), "64738")
+}
+
 func handle_raw_error(e error) {
 	fmt.Fprintf(os.Stderr, "%s\n", e.Error())
 	os.Exit(1)