diff --git a/uuid.go b/uuid.go
index a841946..38c59b2 100644
--- a/uuid.go
+++ b/uuid.go
@@ -36,10 +36,10 @@ type UUID [16]byte
 
 // Predefined namespace UUIDs.
 var (
-	NamespaceDNS  = UUID{0x6b, 0xa7, 0xb8, 0x10, 0x9d, 0xad, 0x11, 0xd1, 0x80, 0xb4, 0x00, 0xc0, 0x4f, 0xd4, 0x30, 0xc8}
-	NamespaceURL  = UUID{0x6b, 0xa7, 0xb8, 0x11, 0x9d, 0xad, 0x11, 0xd1, 0x80, 0xb4, 0x00, 0xc0, 0x4f, 0xd4, 0x30, 0xc8}
-	NamespaceOID  = UUID{0x6b, 0xa7, 0xb8, 0x12, 0x9d, 0xad, 0x11, 0xd1, 0x80, 0xb4, 0x00, 0xc0, 0x4f, 0xd4, 0x30, 0xc8}
-	NamespaceX500 = UUID{0x6b, 0xa7, 0xb8, 0x14, 0x9d, 0xad, 0x11, 0xd1, 0x80, 0xb4, 0x00, 0xc0, 0x4f, 0xd4, 0x30, 0xc8}
+	NamespaceDNS  = &UUID{0x6b, 0xa7, 0xb8, 0x10, 0x9d, 0xad, 0x11, 0xd1, 0x80, 0xb4, 0x00, 0xc0, 0x4f, 0xd4, 0x30, 0xc8}
+	NamespaceURL  = &UUID{0x6b, 0xa7, 0xb8, 0x11, 0x9d, 0xad, 0x11, 0xd1, 0x80, 0xb4, 0x00, 0xc0, 0x4f, 0xd4, 0x30, 0xc8}
+	NamespaceOID  = &UUID{0x6b, 0xa7, 0xb8, 0x12, 0x9d, 0xad, 0x11, 0xd1, 0x80, 0xb4, 0x00, 0xc0, 0x4f, 0xd4, 0x30, 0xc8}
+	NamespaceX500 = &UUID{0x6b, 0xa7, 0xb8, 0x14, 0x9d, 0xad, 0x11, 0xd1, 0x80, 0xb4, 0x00, 0xc0, 0x4f, 0xd4, 0x30, 0xc8}
 )
 
 // Returns algorithm version used to generate UUID.
@@ -110,7 +110,7 @@ func NewV1() (u *UUID, err error) {
 }
 
 // Returns UUID based on MD5 hash of namespace UUID and name.
-func NewV3(ns UUID, name string) (u *UUID, err error) {
+func NewV3(ns *UUID, name string) (u *UUID, err error) {
 	u, err = newFromHash(md5.New(), ns, name)
 	if err != nil {
 		return
@@ -133,7 +133,7 @@ func NewV4() (u *UUID, err error) {
 }
 
 // Returns UUID based on SHA-1 hash of namespace UUID and name.
-func NewV5(ns UUID, name string) (u *UUID, err error) {
+func NewV5(ns *UUID, name string) (u *UUID, err error) {
 	u, err = newFromHash(sha1.New(), ns, name)
 	if err != nil {
 		return
@@ -144,7 +144,7 @@ func NewV5(ns UUID, name string) (u *UUID, err error) {
 }
 
 // Returns UUID based on hashing of namespace UUID and name.
-func newFromHash(h hash.Hash, ns UUID, name string) (u *UUID, err error) {
+func newFromHash(h hash.Hash, ns *UUID, name string) (u *UUID, err error) {
 	u = new(UUID)
 	h.Write(ns[:])
 	h.Write([]byte(name))