diff --git a/internal/utils/ip.go b/internal/utils/ip.go
new file mode 100644
index 00000000..7ac7ffec
--- /dev/null
+++ b/internal/utils/ip.go
@@ -0,0 +1,10 @@
+package utils
+
+import "net"
+
+func IsIPv4(ip net.IP) bool {
+	// If ip is not an IPv4 address, To4 returns nil.
+	// Note that there might be some corner cases, where this is not correct.
+	// See https://stackoverflow.com/questions/22751035/golang-distinguish-ipv4-ipv6.
+	return ip.To4() != nil
+}
diff --git a/internal/utils/ip_test.go b/internal/utils/ip_test.go
new file mode 100644
index 00000000..b61cf529
--- /dev/null
+++ b/internal/utils/ip_test.go
@@ -0,0 +1,17 @@
+package utils
+
+import (
+	"net"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("IP", func() {
+	It("tells IPv4 and IPv6 addresses apart", func() {
+		Expect(IsIPv4(net.IPv4(127, 0, 0, 1))).To(BeTrue())
+		Expect(IsIPv4(net.IPv4zero)).To(BeTrue())
+		Expect(IsIPv4(net.IPv6zero)).To(BeFalse())
+		Expect(IsIPv4(net.IPv6loopback)).To(BeFalse())
+	})
+})
diff --git a/metrics/metrics.go b/metrics/metrics.go
index f764d025..e9bdac5d 100644
--- a/metrics/metrics.go
+++ b/metrics/metrics.go
@@ -6,6 +6,8 @@ import (
 	"net"
 	"time"
 
+	"github.com/lucas-clemente/quic-go/internal/utils"
+
 	"github.com/lucas-clemente/quic-go/internal/protocol"
 	"github.com/lucas-clemente/quic-go/logging"
 
@@ -118,13 +120,10 @@ func (t *connTracer) StartedConnection(local, _ net.Addr, _ logging.VersionNumbe
 
 	var ipVersionTag tag.Mutator
 	if udpAddr, ok := local.(*net.UDPAddr); ok {
-		// If ip is not an IPv4 address, To4 returns nil.
-		// Note that there might be some corner cases, where this is not correct.
-		// See https://stackoverflow.com/questions/22751035/golang-distinguish-ipv4-ipv6.
-		if udpAddr.IP.To4() == nil {
-			ipVersionTag = tag.Upsert(keyIPVersion, "IPv6")
-		} else {
+		if utils.IsIPv4(udpAddr.IP) {
 			ipVersionTag = tag.Upsert(keyIPVersion, "IPv4")
+		} else {
+			ipVersionTag = tag.Upsert(keyIPVersion, "IPv6")
 		}
 	} else {
 		ipVersionTag = tag.Upsert(keyIPVersion, "unknown")
diff --git a/packet_packer.go b/packet_packer.go
index b1dea6f2..cdb39e9a 100644
--- a/packet_packer.go
+++ b/packet_packer.go
@@ -110,13 +110,10 @@ func getMaxPacketSize(addr net.Addr) protocol.ByteCount {
 	// If this is not a UDP address, we don't know anything about the MTU.
 	// Use the minimum size of an Initial packet as the max packet size.
 	if udpAddr, ok := addr.(*net.UDPAddr); ok {
-		// If ip is not an IPv4 address, To4 returns nil.
-		// Note that there might be some corner cases, where this is not correct.
-		// See https://stackoverflow.com/questions/22751035/golang-distinguish-ipv4-ipv6.
-		if udpAddr.IP.To4() == nil {
-			maxSize = protocol.MaxPacketSizeIPv6
-		} else {
+		if utils.IsIPv4(udpAddr.IP) {
 			maxSize = protocol.MaxPacketSizeIPv4
+		} else {
+			maxSize = protocol.MaxPacketSizeIPv6
 		}
 	}
 	return maxSize
diff --git a/qlog/event.go b/qlog/event.go
index 4883e770..f06c99ee 100644
--- a/qlog/event.go
+++ b/qlog/event.go
@@ -5,6 +5,8 @@ import (
 	"net"
 	"time"
 
+	"github.com/lucas-clemente/quic-go/internal/utils"
+
 	"github.com/lucas-clemente/quic-go/internal/protocol"
 	"github.com/lucas-clemente/quic-go/logging"
 
@@ -75,14 +77,10 @@ func (e eventConnectionStarted) Name() string       { return "connection_started
 func (e eventConnectionStarted) IsNil() bool        { return false }
 
 func (e eventConnectionStarted) MarshalJSONObject(enc *gojay.Encoder) {
-	// If ip is not an IPv4 address, To4 returns nil.
-	// Note that there might be some corner cases, where this is not correct.
-	// See https://stackoverflow.com/questions/22751035/golang-distinguish-ipv4-ipv6.
-	isIPv6 := e.SrcAddr.IP.To4() == nil
-	if isIPv6 {
-		enc.StringKey("ip_version", "ipv6")
-	} else {
+	if utils.IsIPv4(e.SrcAddr.IP) {
 		enc.StringKey("ip_version", "ipv4")
+	} else {
+		enc.StringKey("ip_version", "ipv6")
 	}
 	enc.StringKey("src_ip", e.SrcAddr.IP.String())
 	enc.IntKey("src_port", e.SrcAddr.Port)