diff --git a/crypto_stream.go b/crypto_stream.go
index 7f43a2a2..d399d37d 100644
--- a/crypto_stream.go
+++ b/crypto_stream.go
@@ -6,6 +6,7 @@ import (
 	"io"
 
 	"github.com/lucas-clemente/quic-go/internal/protocol"
+	"github.com/lucas-clemente/quic-go/internal/qerr"
 	"github.com/lucas-clemente/quic-go/internal/utils"
 	"github.com/lucas-clemente/quic-go/internal/wire"
 )
@@ -73,7 +74,7 @@ func (s *cryptoStreamImpl) HandleCryptoFrame(f *wire.CryptoFrame) error {
 	if s.finished {
 		if highestOffset > s.highestOffset {
 			// reject crypto data received after this stream was already finished
-			return errors.New("received crypto data after change of encryption level")
+			return qerr.Error(qerr.ProtocolViolation, "received crypto data after change of encryption level")
 		}
 		// ignore data with a smaller offset than the highest received
 		// could e.g. be a retransmission
diff --git a/crypto_stream_test.go b/crypto_stream_test.go
index 834bbd5f..9467f798 100644
--- a/crypto_stream_test.go
+++ b/crypto_stream_test.go
@@ -119,7 +119,7 @@ var _ = Describe("Crypto Stream", func() {
 				err := str.HandleCryptoFrame(&wire.CryptoFrame{
 					Data: createHandshakeMessage(5),
 				})
-				Expect(err).To(MatchError("received crypto data after change of encryption level"))
+				Expect(err).To(MatchError("PROTOCOL_VIOLATION: received crypto data after change of encryption level"))
 			})
 
 			It("ignores crypto data below the maximum offset received before finishing", func() {