diff --git a/headerv2.go b/headerv2.go
index e3565bf..032f90e 100644
--- a/headerv2.go
+++ b/headerv2.go
@@ -50,7 +50,24 @@ func parseV2(r *bufio.Reader) (*HeaderV2, error) {
 	}
 
 	// highest 4 indicate address family
-	if (rawHdr.FamProto >> 4) > 3 {
+	switch rawHdr.FamProto >> 4 {
+	case 0: // local
+		if rawHdr.Len != 0 {
+			return nil, &InvalidHeaderErr{Read: buf[:16], error: errors.New("invalid length")}
+		}
+	case 1: // ipv4
+		if rawHdr.Len != 12 {
+			return nil, &InvalidHeaderErr{Read: buf[:16], error: errors.New("invalid length")}
+		}
+	case 2: // ipv6
+		if rawHdr.Len != 36 {
+			return nil, &InvalidHeaderErr{Read: buf[:16], error: errors.New("invalid length")}
+		}
+	case 3: // unix
+		if rawHdr.Len != 216 {
+			return nil, &InvalidHeaderErr{Read: buf[:16], error: errors.New("invalid length")}
+		}
+	default:
 		return nil, &InvalidHeaderErr{Read: buf[:16], error: errors.New("invalid v2 address family")}
 	}
 
@@ -59,13 +76,7 @@ func parseV2(r *bufio.Reader) (*HeaderV2, error) {
 		return nil, &InvalidHeaderErr{Read: buf[:16], error: errors.New("invalid v2 transport protocol")}
 	}
 
-	if 16+int(rawHdr.Len) > len(buf) {
-		newBuf := make([]byte, 16+int(rawHdr.Len))
-		copy(newBuf, buf[:16])
-		buf = newBuf
-	} else {
-		buf = buf[:16+int(rawHdr.Len)]
-	}
+	buf = buf[:16+int(rawHdr.Len)]
 
 	n, err = io.ReadFull(r, buf[16:])
 	if err != nil {
diff --git a/headerv2_test.go b/headerv2_test.go
index 352c8b5..42ac127 100644
--- a/headerv2_test.go
+++ b/headerv2_test.go
@@ -33,7 +33,9 @@ func TestHeaderV2(t *testing.T) {
 				buf.Write(s.value)
 			}
 			hdr, err := Parse(bufio.NewReader(&buf))
-			assert.NoError(t, err)
+			if !assert.NoError(t, err) {
+				return
+			}
 			assert.IsType(t, &HeaderV2{}, hdr, "Header Type")
 			p := hdr.(*HeaderV2)
 			assert.Equal(t, h.Command, p.Command, "Command")
diff --git a/parse_test.go b/parse_test.go
new file mode 100644
index 0000000..48e2eaa
--- /dev/null
+++ b/parse_test.go
@@ -0,0 +1,28 @@
+package proxyprotocol
+
+import (
+	"bufio"
+	"bytes"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestParse_Malformed(t *testing.T) {
+	data := []byte{
+		// PROXY protocol v2 magic header
+		0x0D, 0x0A, 0x0D, 0x0A, 0x00, 0x0D, 0x0A, 0x51, 0x55, 0x49, 0x54, 0x0A,
+		// v2 version, PROXY cmd
+		0x21,
+		// TCP, IPv4 (also works with 0x13,0x21,0x22,0x31,0x32)
+		0x12,
+		// Length
+		0x00, 0x00,
+		// src/dest address data _should_ be here but is omitted.
+	}
+
+	_, err := Parse(
+		bufio.NewReader(
+			bytes.NewReader(data)))
+	assert.Error(t, err)
+}