diff --git a/conn_id_manager.go b/conn_id_manager.go
index ee1729a74..92bffe206 100644
--- a/conn_id_manager.go
+++ b/conn_id_manager.go
@@ -70,7 +70,7 @@ func (h *connIDManager) Add(f *wire.NewConnectionIDFrame) error {
 func (h *connIDManager) add(f *wire.NewConnectionIDFrame) error {
 	// If the NEW_CONNECTION_ID frame is reordered, such that its sequence number is smaller than the currently active
 	// connection ID or if it was already retired, send the RETIRE_CONNECTION_ID frame immediately.
-	if f.SequenceNumber <= h.activeSequenceNumber || f.SequenceNumber < h.highestRetired {
+	if f.SequenceNumber < h.activeSequenceNumber || f.SequenceNumber < h.highestRetired {
 		h.queueControlFrame(&wire.RetireConnectionIDFrame{
 			SequenceNumber: f.SequenceNumber,
 		})
diff --git a/conn_id_manager_test.go b/conn_id_manager_test.go
index 3c3a6cfb1..34243f6fc 100644
--- a/conn_id_manager_test.go
+++ b/conn_id_manager_test.go
@@ -201,6 +201,27 @@ var _ = Describe("Connection ID Manager", func() {
 		Expect(frameQueue[0].(*wire.RetireConnectionIDFrame).SequenceNumber).To(BeEquivalentTo(9))
 	})
 
+	It("accepts retransmissions for the connection ID that is in use", func() {
+		connID := protocol.ConnectionID{1, 2, 3, 4}
+
+		Expect(m.Add(&wire.NewConnectionIDFrame{
+			SequenceNumber: 1,
+			ConnectionID:   connID,
+		})).To(Succeed())
+		Expect(frameQueue).To(BeEmpty())
+		Expect(m.Get()).To(Equal(connID))
+		Expect(frameQueue).To(HaveLen(1))
+		Expect(frameQueue[0]).To(BeAssignableToTypeOf(&wire.RetireConnectionIDFrame{}))
+		Expect(frameQueue[0].(*wire.RetireConnectionIDFrame).SequenceNumber).To(BeZero())
+		frameQueue = nil
+
+		Expect(m.Add(&wire.NewConnectionIDFrame{
+			SequenceNumber: 1,
+			ConnectionID:   connID,
+		})).To(Succeed())
+		Expect(frameQueue).To(BeEmpty())
+	})
+
 	It("errors when the peer sends too connection IDs", func() {
 		for i := uint8(1); i < protocol.MaxActiveConnectionIDs; i++ {
 			Expect(m.Add(&wire.NewConnectionIDFrame{