diff --git a/conn_id_generator.go b/conn_id_generator.go
index ab748f1af..a95110af8 100644
--- a/conn_id_generator.go
+++ b/conn_id_generator.go
@@ -18,6 +18,7 @@ type connIDGenerator struct {
 	addConnectionID    func(protocol.ConnectionID) [16]byte
 	removeConnectionID func(protocol.ConnectionID)
 	retireConnectionID func(protocol.ConnectionID)
+	replaceWithClosed  func(protocol.ConnectionID, packetHandler)
 	queueControlFrame  func(wire.Frame)
 }
 
@@ -26,6 +27,7 @@ func newConnIDGenerator(
 	addConnectionID func(protocol.ConnectionID) [16]byte,
 	removeConnectionID func(protocol.ConnectionID),
 	retireConnectionID func(protocol.ConnectionID),
+	replaceWithClosed func(protocol.ConnectionID, packetHandler),
 	queueControlFrame func(wire.Frame),
 ) *connIDGenerator {
 	m := &connIDGenerator{
@@ -34,6 +36,7 @@ func newConnIDGenerator(
 		addConnectionID:    addConnectionID,
 		removeConnectionID: removeConnectionID,
 		retireConnectionID: retireConnectionID,
+		replaceWithClosed:  replaceWithClosed,
 		queueControlFrame:  queueControlFrame,
 	}
 	m.activeSrcConnIDs[0] = initialConnectionID
@@ -93,3 +96,9 @@ func (m *connIDGenerator) RemoveAll() {
 		m.removeConnectionID(connID)
 	}
 }
+
+func (m *connIDGenerator) ReplaceWithClosed(handler packetHandler) {
+	for _, connID := range m.activeSrcConnIDs {
+		m.replaceWithClosed(connID, handler)
+	}
+}
diff --git a/conn_id_generator_test.go b/conn_id_generator_test.go
index c775d694f..81b363063 100644
--- a/conn_id_generator_test.go
+++ b/conn_id_generator_test.go
@@ -10,20 +10,23 @@ import (
 
 var _ = Describe("Connection ID Generator", func() {
 	var (
-		addedConnIDs   []protocol.ConnectionID
-		retiredConnIDs []protocol.ConnectionID
-		removedConnIDs []protocol.ConnectionID
-		queuedFrames   []wire.Frame
-		g              *connIDGenerator
+		addedConnIDs       []protocol.ConnectionID
+		retiredConnIDs     []protocol.ConnectionID
+		removedConnIDs     []protocol.ConnectionID
+		replacedWithClosed map[string]packetHandler
+		queuedFrames       []wire.Frame
+		g                  *connIDGenerator
 	)
+	initialConnID := protocol.ConnectionID{1, 2, 3, 4, 5, 6, 7}
 
 	BeforeEach(func() {
 		addedConnIDs = nil
 		retiredConnIDs = nil
 		removedConnIDs = nil
 		queuedFrames = nil
+		replacedWithClosed = make(map[string]packetHandler)
 		g = newConnIDGenerator(
-			protocol.ConnectionID{1, 2, 3, 4, 5, 6, 7},
+			initialConnID,
 			func(c protocol.ConnectionID) [16]byte {
 				addedConnIDs = append(addedConnIDs, c)
 				l := uint8(len(addedConnIDs))
@@ -31,6 +34,7 @@ var _ = Describe("Connection ID Generator", func() {
 			},
 			func(c protocol.ConnectionID) { removedConnIDs = append(removedConnIDs, c) },
 			func(c protocol.ConnectionID) { retiredConnIDs = append(retiredConnIDs, c) },
+			func(c protocol.ConnectionID, h packetHandler) { replacedWithClosed[string(c)] = h },
 			func(f wire.Frame) { queuedFrames = append(queuedFrames, f) },
 		)
 	})
@@ -81,7 +85,7 @@ var _ = Describe("Connection ID Generator", 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(retiredConnIDs[0]).To(Equal(initialConnID))
 		Expect(addedConnIDs).To(BeEmpty())
 	})
 
@@ -101,11 +105,24 @@ var _ = Describe("Connection ID Generator", 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
+		Expect(removedConnIDs).To(HaveLen(6)) // initial connection ID and newly issued ones
+		Expect(removedConnIDs).To(ContainElement(initialConnID))
 		for _, f := range queuedFrames {
 			nf := f.(*wire.NewConnectionIDFrame)
 			Expect(removedConnIDs).To(ContainElement(nf.ConnectionID))
 		}
 	})
+
+	It("replaces with a closed session for all connection IDs", func() {
+		Expect(g.SetMaxActiveConnIDs(5)).To(Succeed())
+		Expect(queuedFrames).To(HaveLen(5))
+		sess := NewMockPacketHandler(mockCtrl)
+		g.ReplaceWithClosed(sess)
+		Expect(replacedWithClosed).To(HaveLen(6)) // initial connection ID and newly issued ones
+		Expect(replacedWithClosed).To(HaveKeyWithValue(string(initialConnID), sess))
+		for _, f := range queuedFrames {
+			nf := f.(*wire.NewConnectionIDFrame)
+			Expect(replacedWithClosed).To(HaveKeyWithValue(string(nf.ConnectionID), sess))
+		}
+	})
 })