diff --git a/frames/ack_frame.go b/frames/ack_frame.go
index e7e1295c..90b67b78 100644
--- a/frames/ack_frame.go
+++ b/frames/ack_frame.go
@@ -2,6 +2,7 @@ package frames
 
 import (
 	"bytes"
+	"fmt"
 
 	"github.com/lucas-clemente/quic-go/protocol"
 	"github.com/lucas-clemente/quic-go/utils"
@@ -36,8 +37,9 @@ func ParseAckFrame(r *bytes.Reader) (*AckFrame, error) {
 		return nil, err
 	}
 
+	hasNACK := false
 	if typeByte&0x20 == 0x20 {
-		panic("NACK ranges not yet implemented.")
+		hasNACK = true
 	}
 	if typeByte&0x10 == 0x10 {
 		panic("truncated ACKs not yet implemented.")
@@ -94,11 +96,27 @@ func ParseAckFrame(r *bytes.Reader) (*AckFrame, error) {
 			return nil, err
 		}
 		// Time Since Previous Timestamp
-		_, err := utils.ReadUint16(r)
+		_, err = utils.ReadUint16(r)
 		if err != nil {
 			return nil, err
 		}
 	}
 
+	if hasNACK {
+		fmt.Println("NACK not implemented yet!")
+		var numRanges uint8
+		numRanges, err = r.ReadByte()
+		if err != nil {
+			return nil, err
+		}
+		p := make([]byte, largestObservedLen+1)
+		for i := uint8(0); i < numRanges; i++ {
+			_, err := r.Read(p)
+			if err != nil {
+				return nil, err
+			}
+		}
+	}
+
 	return frame, nil
 }
diff --git a/session.go b/session.go
index 34905037..2fe31098 100644
--- a/session.go
+++ b/session.go
@@ -105,9 +105,9 @@ func (s *Session) HandlePacket(addr *net.UDPAddr, publicHeaderBinary []byte, pub
 		err = nil
 		if typeByte&0x80 == 0x80 {
 			err = s.handleStreamFrame(r)
-		} else if typeByte == 0x40 {
+		} else if typeByte&0xca == 0x40 {
 			err = s.handleAckFrame(r)
-		} else if typeByte&0xE0 == 0x20 {
+		} else if typeByte&0xe0 == 0x20 {
 			err = errors.New("unimplemented: CONGESTION_FEEDBACK")
 		} else {
 			switch typeByte {
@@ -120,9 +120,15 @@ func (s *Session) HandlePacket(addr *net.UDPAddr, publicHeaderBinary []byte, pub
 			case 0x03:
 				err = errors.New("unimplemented: GOAWAY")
 			case 0x04:
-				err = errors.New("unimplemented: WINDOW_UPDATE")
+				// err = errors.New("unimplemented: WINDOW_UPDATE")
+				fmt.Println("unimplemented: WINDOW_UPDATE")
+				p := make([]byte, 1+4+8)
+				_, err = r.Read(p)
 			case 0x05:
-				err = errors.New("unimplemented: BLOCKED")
+				// err = errors.New("unimplemented: BLOCKED")
+				fmt.Println("unimplemented: BLOCKED")
+				p := make([]byte, 1+4)
+				_, err = r.Read(p)
 			case 0x06:
 				err = s.handleStopWaitingFrame(r, publicHeader)
 			case 0x07: