diff --git a/conn_id_generator.go b/conn_id_generator.go
index 7bcc3581..ff961508 100644
--- a/conn_id_generator.go
+++ b/conn_id_generator.go
@@ -77,7 +77,7 @@ func (m *connIDGenerator) Retire(seq uint64, sentWithDestConnID protocol.Connect
 		return nil
 	}
 	if connID.Equal(sentWithDestConnID) {
-		return qerr.NewError(qerr.FrameEncodingError, fmt.Sprintf("tried to retire connection ID %d (%s), which was used as the Destination Connection ID on this packet", seq, connID))
+		return qerr.NewError(qerr.ProtocolViolation, fmt.Sprintf("tried to retire connection ID %d (%s), which was used as the Destination Connection ID on this packet", seq, connID))
 	}
 	m.retireConnectionID(connID)
 	delete(m.activeSrcConnIDs, seq)
diff --git a/conn_id_generator_test.go b/conn_id_generator_test.go
index 7b51b480..fc36c766 100644
--- a/conn_id_generator_test.go
+++ b/conn_id_generator_test.go
@@ -78,7 +78,7 @@ var _ = Describe("Connection ID Generator", func() {
 		Expect(queuedFrames).ToNot(BeEmpty())
 		Expect(queuedFrames[0]).To(BeAssignableToTypeOf(&wire.NewConnectionIDFrame{}))
 		f := queuedFrames[0].(*wire.NewConnectionIDFrame)
-		Expect(g.Retire(f.SequenceNumber, f.ConnectionID)).To(MatchError(fmt.Sprintf("FRAME_ENCODING_ERROR: tried to retire connection ID %d (%s), which was used as the Destination Connection ID on this packet", f.SequenceNumber, f.ConnectionID)))
+		Expect(g.Retire(f.SequenceNumber, f.ConnectionID)).To(MatchError(fmt.Sprintf("PROTOCOL_VIOLATION: tried to retire connection ID %d (%s), which was used as the Destination Connection ID on this packet", f.SequenceNumber, f.ConnectionID)))
 	})
 
 	It("issues new connection IDs, when old ones are retired", func() {