diff --git a/internal/protocol/protocol.go b/internal/protocol/protocol.go
index 98bc9ffb..b8104882 100644
--- a/internal/protocol/protocol.go
+++ b/internal/protocol/protocol.go
@@ -43,6 +43,21 @@ const (
 	ECNCE             // 11
 )
 
+func (e ECN) String() string {
+	switch e {
+	case ECNNon:
+		return "Not-ECT"
+	case ECT1:
+		return "ECT(1)"
+	case ECT0:
+		return "ECT(0)"
+	case ECNCE:
+		return "CE"
+	default:
+		return fmt.Sprintf("invalid ECN value: %d", e)
+	}
+}
+
 // A ByteCount in QUIC
 type ByteCount int64
 
diff --git a/internal/protocol/protocol_test.go b/internal/protocol/protocol_test.go
index d9048f01..e672d31e 100644
--- a/internal/protocol/protocol_test.go
+++ b/internal/protocol/protocol_test.go
@@ -22,4 +22,12 @@ var _ = Describe("Protocol", func() {
 		Expect(ECN(0b00000001)).To(Equal(ECT1))
 		Expect(ECN(0b00000011)).To(Equal(ECNCE))
 	})
+
+	It("has a string representation for ECN", func() {
+		Expect(ECNNon.String()).To(Equal("Not-ECT"))
+		Expect(ECT0.String()).To(Equal("ECT(0)"))
+		Expect(ECT1.String()).To(Equal("ECT(1)"))
+		Expect(ECNCE.String()).To(Equal("CE"))
+		Expect(ECN(42).String()).To(Equal("invalid ECN value: 42"))
+	})
 })