diff --git a/runner/runner.go b/runner/runner.go
index 1bf2b7f..8b9642f 100644
--- a/runner/runner.go
+++ b/runner/runner.go
@@ -8,6 +8,7 @@ import (
 	"net"
 	"net/http"
 	"strconv"
+	"strings"
 	"time"
 
 	"github.com/gotify/server/v2/config"
@@ -75,7 +76,11 @@ func redirectToHTTPS(port string) http.HandlerFunc {
 func changePort(hostPort, port string) string {
 	host, _, err := net.SplitHostPort(hostPort)
 	if err != nil {
-		return hostPort
+		// There is no exported error.
+		if !strings.Contains(err.Error(), "missing port") {
+			return hostPort
+		}
+		host = hostPort
 	}
 	return net.JoinHostPort(host, port)
 }
diff --git a/runner/runner_test.go b/runner/runner_test.go
new file mode 100644
index 0000000..fa22255
--- /dev/null
+++ b/runner/runner_test.go
@@ -0,0 +1,35 @@
+package runner
+
+import (
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestRedirect(t *testing.T) {
+	cases := []struct {
+		Request string
+		TLS     int
+		Expect  string
+	}{
+		{Request: "http://gotify.net/meow", TLS: 443, Expect: "https://gotify.net:443/meow"},
+		{Request: "http://gotify.net:8080/meow", TLS: 443, Expect: "https://gotify.net:443/meow"},
+		{Request: "http://gotify.net:8080/meow", TLS: 8443, Expect: "https://gotify.net:8443/meow"},
+	}
+
+	for _, testCase := range cases {
+		name := fmt.Sprintf("%s -- %d -> %s", testCase.Request, testCase.TLS, testCase.Expect)
+		t.Run(name, func(t *testing.T) {
+			req := httptest.NewRequest("GET", testCase.Request, nil)
+			rec := httptest.NewRecorder()
+
+			redirectToHTTPS(fmt.Sprint(testCase.TLS)).ServeHTTP(rec, req)
+
+			assert.Equal(t, http.StatusFound, rec.Result().StatusCode)
+			assert.Equal(t, testCase.Expect, rec.Header().Get("location"))
+		})
+	}
+}