diff --git a/packet_handler_map.go b/packet_handler_map.go
index 0f77dd9de8c..114d2a18e03 100644
--- a/packet_handler_map.go
+++ b/packet_handler_map.go
@@ -173,6 +173,14 @@ func (h *packetHandlerMap) handlePacket(
 		return fmt.Errorf("error parsing header: %s", err)
 	}
 
+	if hdr.IsLongHeader {
+		if protocol.ByteCount(r.Len()) < hdr.Length {
+			return fmt.Errorf("packet length (%d bytes) is smaller than the expected length (%d bytes)", len(data)-int(hdr.ParsedLen()), hdr.Length)
+		}
+		data = data[:int(hdr.ParsedLen()+hdr.Length)]
+		// TODO(#1312): implement parsing of compound packets
+	}
+
 	p := &receivedPacket{
 		remoteAddr: addr,
 		hdr:        hdr,
diff --git a/packet_handler_map_test.go b/packet_handler_map_test.go
index 31bc7513f51..8a0141d3d98 100644
--- a/packet_handler_map_test.go
+++ b/packet_handler_map_test.go
@@ -19,21 +19,25 @@ var _ = Describe("Packet Handler Map", func() {
 		conn    *mockPacketConn
 	)
 
-	getPacket := func(connID protocol.ConnectionID) []byte {
+	getPacketWithLength := func(connID protocol.ConnectionID, length protocol.ByteCount) []byte {
 		buf := &bytes.Buffer{}
 		Expect((&wire.ExtendedHeader{
 			Header: wire.Header{
 				IsLongHeader:     true,
 				Type:             protocol.PacketTypeHandshake,
 				DestConnectionID: connID,
-				Length:           1,
+				Length:           length,
 				Version:          protocol.VersionTLS,
 			},
-			PacketNumberLen: protocol.PacketNumberLen1,
+			PacketNumberLen: protocol.PacketNumberLen2,
 		}).Write(buf, protocol.VersionWhatever)).To(Succeed())
 		return buf.Bytes()
 	}
 
+	getPacket := func(connID protocol.ConnectionID) []byte {
+		return getPacketWithLength(connID, 1)
+	}
+
 	BeforeEach(func() {
 		conn = newMockPacketConn()
 		handler = newPacketHandlerMap(conn, 5, utils.DefaultLogger).(*packetHandlerMap)
@@ -131,6 +135,24 @@ var _ = Describe("Packet Handler Map", func() {
 			conn.Close()
 			Eventually(done).Should(BeClosed())
 		})
+
+		It("errors on packets that are smaller than the length in the packet header", func() {
+			connID := protocol.ConnectionID{1, 2, 3, 4, 5, 6, 7, 8}
+			data := append(getPacketWithLength(connID, 1000), make([]byte, 500-2 /* for packet number length */)...)
+			err := handler.handlePacket(nil, nil, data)
+			Expect(err).To(MatchError("packet length (500 bytes) is smaller than the expected length (1000 bytes)"))
+		})
+
+		It("cuts packets to the right length", func() {
+			connID := protocol.ConnectionID{1, 2, 3, 4, 5, 6, 7, 8}
+			data := append(getPacketWithLength(connID, 456), make([]byte, 1000)...)
+			packetHandler := NewMockPacketHandler(mockCtrl)
+			packetHandler.EXPECT().handlePacket(gomock.Any()).Do(func(p *receivedPacket) {
+				Expect(p.data).To(HaveLen(456 + int(p.hdr.ParsedLen())))
+			})
+			handler.Add(connID, packetHandler)
+			Expect(handler.handlePacket(nil, nil, data)).To(Succeed())
+		})
 	})
 
 	Context("stateless reset handling", func() {
diff --git a/packet_unpacker.go b/packet_unpacker.go
index b9eb8ea0154..cda22232466 100644
--- a/packet_unpacker.go
+++ b/packet_unpacker.go
@@ -39,14 +39,6 @@ func newPacketUnpacker(cs handshake.CryptoSetup, version protocol.VersionNumber)
 func (u *packetUnpacker) Unpack(hdr *wire.Header, data []byte) (*unpackedPacket, error) {
 	r := bytes.NewReader(data)
 
-	if hdr.IsLongHeader {
-		if protocol.ByteCount(r.Len()) < hdr.Length {
-			return nil, fmt.Errorf("packet length (%d bytes) is smaller than the expected length (%d bytes)", len(data)-int(hdr.ParsedLen()), hdr.Length)
-		}
-		data = data[:int(hdr.ParsedLen()+hdr.Length)]
-		// TODO(#1312): implement parsing of compound packets
-	}
-
 	var encLevel protocol.EncryptionLevel
 	switch hdr.Type {
 	case protocol.PacketTypeInitial:
diff --git a/packet_unpacker_test.go b/packet_unpacker_test.go
index 8aa4e446b9b..c9a085d08f7 100644
--- a/packet_unpacker_test.go
+++ b/packet_unpacker_test.go
@@ -75,49 +75,6 @@ var _ = Describe("Packet Unpacker", func() {
 		Expect(packet.encryptionLevel).To(Equal(protocol.EncryptionInitial))
 	})
 
-	It("errors on packets that are smaller than the length in the packet header", func() {
-		extHdr := &wire.ExtendedHeader{
-			Header: wire.Header{
-				IsLongHeader:     true,
-				Type:             protocol.PacketTypeHandshake,
-				Length:           1000,
-				DestConnectionID: connID,
-				Version:          version,
-			},
-			PacketNumberLen: protocol.PacketNumberLen2,
-		}
-		hdr, hdrRaw := getHeader(extHdr)
-		data := append(hdrRaw, make([]byte, 500-2 /* for packet number length */)...)
-		_, err := unpacker.Unpack(hdr, data)
-		Expect(err).To(MatchError("packet length (500 bytes) is smaller than the expected length (1000 bytes)"))
-	})
-
-	It("cuts packets to the right length", func() {
-		pnLen := protocol.PacketNumberLen2
-		extHdr := &wire.ExtendedHeader{
-			Header: wire.Header{
-				IsLongHeader:     true,
-				DestConnectionID: connID,
-				Type:             protocol.PacketTypeHandshake,
-				Length:           456,
-				Version:          protocol.VersionTLS,
-			},
-			PacketNumberLen: pnLen,
-		}
-		payloadLen := 456 - int(pnLen)
-		hdr, hdrRaw := getHeader(extHdr)
-		data := append(hdrRaw, make([]byte, payloadLen)...)
-		opener := mocks.NewMockOpener(mockCtrl)
-		cs.EXPECT().GetOpener(protocol.EncryptionHandshake).Return(opener, nil)
-		opener.EXPECT().DecryptHeader(gomock.Any(), gomock.Any(), gomock.Any())
-		opener.EXPECT().Open(gomock.Any(), gomock.Any(), extHdr.PacketNumber, hdrRaw).DoAndReturn(func(_, payload []byte, _ protocol.PacketNumber, _ []byte) ([]byte, error) {
-			Expect(payload).To(HaveLen(payloadLen))
-			return []byte{0}, nil
-		})
-		_, err := unpacker.Unpack(hdr, data)
-		Expect(err).ToNot(HaveOccurred())
-	})
-
 	It("returns the error when getting the sealer fails", func() {
 		extHdr := &wire.ExtendedHeader{
 			Header:          wire.Header{DestConnectionID: connID},