diff --git a/conn_id_generator.go b/conn_id_generator.go
index caec6b01..ab748f1a 100644
--- a/conn_id_generator.go
+++ b/conn_id_generator.go
@@ -16,6 +16,7 @@ type connIDGenerator struct {
 	activeSrcConnIDs map[uint64]protocol.ConnectionID
 
 	addConnectionID    func(protocol.ConnectionID) [16]byte
+	removeConnectionID func(protocol.ConnectionID)
 	retireConnectionID func(protocol.ConnectionID)
 	queueControlFrame  func(wire.Frame)
 }
@@ -23,6 +24,7 @@ type connIDGenerator struct {
 func newConnIDGenerator(
 	initialConnectionID protocol.ConnectionID,
 	addConnectionID func(protocol.ConnectionID) [16]byte,
+	removeConnectionID func(protocol.ConnectionID),
 	retireConnectionID func(protocol.ConnectionID),
 	queueControlFrame func(wire.Frame),
 ) *connIDGenerator {
@@ -30,6 +32,7 @@ func newConnIDGenerator(
 		connIDLen:          initialConnectionID.Len(),
 		activeSrcConnIDs:   make(map[uint64]protocol.ConnectionID),
 		addConnectionID:    addConnectionID,
+		removeConnectionID: removeConnectionID,
 		retireConnectionID: retireConnectionID,
 		queueControlFrame:  queueControlFrame,
 	}
@@ -84,3 +87,9 @@ func (m *connIDGenerator) issueNewConnID() error {
 	m.highestSeq++
 	return nil
 }
+
+func (m *connIDGenerator) RemoveAll() {
+	for _, connID := range m.activeSrcConnIDs {
+		m.removeConnectionID(connID)
+	}
+}
diff --git a/conn_id_generator_test.go b/conn_id_generator_test.go
index 5d3cec91..c775d694 100644
--- a/conn_id_generator_test.go
+++ b/conn_id_generator_test.go
@@ -12,6 +12,7 @@ var _ = Describe("Connection ID Generator", func() {
 	var (
 		addedConnIDs   []protocol.ConnectionID
 		retiredConnIDs []protocol.ConnectionID
+		removedConnIDs []protocol.ConnectionID
 		queuedFrames   []wire.Frame
 		g              *connIDGenerator
 	)
@@ -19,6 +20,7 @@ var _ = Describe("Connection ID Generator", func() {
 	BeforeEach(func() {
 		addedConnIDs = nil
 		retiredConnIDs = nil
+		removedConnIDs = nil
 		queuedFrames = nil
 		g = newConnIDGenerator(
 			protocol.ConnectionID{1, 2, 3, 4, 5, 6, 7},
@@ -27,6 +29,7 @@ var _ = Describe("Connection ID Generator", func() {
 				l := uint8(len(addedConnIDs))
 				return [16]byte{l, l, l, l, l, l, l, l, l, l, l, l, l, l, l, l}
 			},
+			func(c protocol.ConnectionID) { removedConnIDs = append(removedConnIDs, c) },
 			func(c protocol.ConnectionID) { retiredConnIDs = append(retiredConnIDs, c) },
 			func(f wire.Frame) { queuedFrames = append(queuedFrames, f) },
 		)
@@ -76,6 +79,7 @@ var _ = Describe("Connection ID Generator", func() {
 
 	It("retires the initial connection ID", func() {
 		Expect(g.Retire(0)).To(Succeed())
+		Expect(removedConnIDs).To(BeEmpty())
 		Expect(retiredConnIDs).To(HaveLen(1))
 		Expect(retiredConnIDs[0]).To(Equal(protocol.ConnectionID{1, 2, 3, 4, 5, 6, 7}))
 		Expect(addedConnIDs).To(BeEmpty())
@@ -92,4 +96,16 @@ var _ = Describe("Connection ID Generator", func() {
 		Expect(retiredConnIDs).To(HaveLen(1))
 		Expect(queuedFrames).To(HaveLen(1))
 	})
+
+	It("removes all connection IDs", func() {
+		Expect(g.SetMaxActiveConnIDs(5)).To(Succeed())
+		Expect(queuedFrames).To(HaveLen(5))
+		g.RemoveAll()
+		Expect(removedConnIDs).To(HaveLen(6))                                                 // initial connection ID and newly issued ones
+		Expect(removedConnIDs).To(ContainElement(protocol.ConnectionID{1, 2, 3, 4, 5, 6, 7})) // initial connection ID
+		for _, f := range queuedFrames {
+			nf := f.(*wire.NewConnectionIDFrame)
+			Expect(removedConnIDs).To(ContainElement(nf.ConnectionID))
+		}
+	})
 })