diff --git a/internal/ntp/ntp_test.go b/internal/ntp/ntp_test.go
index 3528b84ce..de88edfc3 100644
--- a/internal/ntp/ntp_test.go
+++ b/internal/ntp/ntp_test.go
@@ -10,7 +10,7 @@ import (
 	"github.com/authelia/authelia/v4/internal/configuration/validator"
 )
 
-func TestShouldCheckNTP(t *testing.T) {
+func TestShouldCheckNTPV4(t *testing.T) {
 	config := &schema.Configuration{
 		NTP: schema.NTPConfiguration{
 			Address:       "time.cloudflare.com:123",
@@ -26,3 +26,20 @@ func TestShouldCheckNTP(t *testing.T) {
 
 	assert.NoError(t, ntp.StartupCheck())
 }
+
+func TestShouldCheckNTPV3(t *testing.T) {
+	config := &schema.Configuration{
+		NTP: schema.NTPConfiguration{
+			Address:       "time.cloudflare.com:123",
+			Version:       3,
+			MaximumDesync: time.Second * 3,
+		},
+	}
+
+	sv := schema.NewStructValidator()
+	validator.ValidateNTP(config, sv)
+
+	ntp := NewProvider(&config.NTP)
+
+	assert.NoError(t, ntp.StartupCheck())
+}
diff --git a/internal/ntp/util_test.go b/internal/ntp/util_test.go
index 53cb9b819..caf07ca02 100644
--- a/internal/ntp/util_test.go
+++ b/internal/ntp/util_test.go
@@ -9,8 +9,33 @@ import (
 	"github.com/authelia/authelia/v4/internal/utils"
 )
 
-func TestShould(t *testing.T) {
+func TestNtpIsOffsetTooLarge(t *testing.T) {
 	maxOffset, _ := utils.ParseDurationString("1s")
 	assert.True(t, ntpIsOffsetTooLarge(maxOffset, time.Now(), time.Now().Add(time.Second*2)))
+	assert.True(t, ntpIsOffsetTooLarge(maxOffset, time.Now().Add(time.Second*2), time.Now()))
 	assert.False(t, ntpIsOffsetTooLarge(maxOffset, time.Now(), time.Now()))
 }
+
+func TestNtpPacketToTime(t *testing.T) {
+	resp := &ntpPacket{
+		TxTimeSeconds:  60,
+		TxTimeFraction: 0,
+	}
+
+	expected := time.Unix(int64(float64(60)-ntpEpochOffset), 0)
+
+	ntpTime := ntpPacketToTime(resp)
+	assert.Equal(t, expected, ntpTime)
+}
+
+func TestLeapVersionClientMode(t *testing.T) {
+	v3Noleap := uint8(27)
+	v4Noleap := uint8(43)
+	v3leap := uint8(91)
+	v4leap := uint8(107)
+
+	assert.Equal(t, v3Noleap, ntpLeapVersionClientMode(false, ntpV3))
+	assert.Equal(t, v4Noleap, ntpLeapVersionClientMode(false, ntpV4))
+	assert.Equal(t, v3leap, ntpLeapVersionClientMode(true, ntpV3))
+	assert.Equal(t, v4leap, ntpLeapVersionClientMode(true, ntpV4))
+}