diff --git a/core/core.go b/core/core.go
index 14112f95793..30106c79413 100644
--- a/core/core.go
+++ b/core/core.go
@@ -58,7 +58,7 @@ type IpfsNode struct {
 	Blocks *bserv.BlockService
 
 	// the merkle dag service, get/add objects.
-	DAG *merkledag.DAGService
+	DAG merkledag.DAGService
 
 	// the path resolution system
 	Resolver *path.Resolver
@@ -161,7 +161,7 @@ func NewIpfsNode(cfg *config.Config, online bool) (*IpfsNode, error) {
 		return nil, err
 	}
 
-	dag := &merkledag.DAGService{Blocks: bs}
+	dag := merkledag.NewDAGService(bs)
 	ns := namesys.NewNameSystem(route)
 	p, err := pin.LoadPinner(d, dag)
 	if err != nil {
diff --git a/core/mock.go b/core/mock.go
index 2257e988543..f35e591f23b 100644
--- a/core/mock.go
+++ b/core/mock.go
@@ -49,7 +49,7 @@ func NewMockNode() (*IpfsNode, error) {
 		return nil, err
 	}
 
-	nd.DAG = &mdag.DAGService{Blocks: bserv}
+	nd.DAG = mdag.NewDAGService(bserv)
 
 	// Namespace resolver
 	nd.Namesys = nsys.NewNameSystem(dht)
diff --git a/merkledag/merkledag.go b/merkledag/merkledag.go
index 7834677a8f8..0e595c9d693 100644
--- a/merkledag/merkledag.go
+++ b/merkledag/merkledag.go
@@ -62,7 +62,7 @@ func MakeLink(n *Node) (*Link, error) {
 	}, nil
 }
 
-func (l *Link) GetNode(serv *DAGService) (*Node, error) {
+func (l *Link) GetNode(serv DAGService) (*Node, error) {
 	if l.Node != nil {
 		return l.Node, nil
 	}
@@ -151,20 +151,32 @@ func (n *Node) Key() (u.Key, error) {
 }
 
 // DAGService is an IPFS Merkle DAG service.
+type DAGService interface {
+	Add(*Node) (u.Key, error)
+	AddRecursive(*Node) error
+	Get(u.Key) (*Node, error)
+	Remove(*Node) error
+}
+
+func NewDAGService(bs *bserv.BlockService) DAGService {
+	return &dagService{bs}
+}
+
+// dagService is an IPFS Merkle DAG service.
 // - the root is virtual (like a forest)
 // - stores nodes' data in a BlockService
 // TODO: should cache Nodes that are in memory, and be
 //       able to free some of them when vm pressure is high
-type DAGService struct {
+type dagService struct {
 	Blocks *bserv.BlockService
 }
 
-// Add adds a node to the DAGService, storing the block in the BlockService
-func (n *DAGService) Add(nd *Node) (u.Key, error) {
+// Add adds a node to the dagService, storing the block in the BlockService
+func (n *dagService) Add(nd *Node) (u.Key, error) {
 	k, _ := nd.Key()
 	log.Debug("DagService Add [%s]", k)
 	if n == nil {
-		return "", fmt.Errorf("DAGService is nil")
+		return "", fmt.Errorf("dagService is nil")
 	}
 
 	d, err := nd.Encoded(false)
@@ -182,7 +194,7 @@ func (n *DAGService) Add(nd *Node) (u.Key, error) {
 	return n.Blocks.AddBlock(b)
 }
 
-func (n *DAGService) AddRecursive(nd *Node) error {
+func (n *dagService) AddRecursive(nd *Node) error {
 	_, err := n.Add(nd)
 	if err != nil {
 		log.Info("AddRecursive Error: %s\n", err)
@@ -201,10 +213,10 @@ func (n *DAGService) AddRecursive(nd *Node) error {
 	return nil
 }
 
-// Get retrieves a node from the DAGService, fetching the block in the BlockService
-func (n *DAGService) Get(k u.Key) (*Node, error) {
+// Get retrieves a node from the dagService, fetching the block in the BlockService
+func (n *dagService) Get(k u.Key) (*Node, error) {
 	if n == nil {
-		return nil, fmt.Errorf("DAGService is nil")
+		return nil, fmt.Errorf("dagService is nil")
 	}
 
 	ctx, _ := context.WithTimeout(context.TODO(), time.Second*5)
@@ -216,7 +228,7 @@ func (n *DAGService) Get(k u.Key) (*Node, error) {
 	return Decoded(b.Data)
 }
 
-func (n *DAGService) Remove(nd *Node) error {
+func (n *dagService) Remove(nd *Node) error {
 	for _, l := range nd.Links {
 		if l.Node != nil {
 			n.Remove(l.Node)
diff --git a/path/path.go b/path/path.go
index 03c1a481e5e..cb1061d1185 100644
--- a/path/path.go
+++ b/path/path.go
@@ -15,7 +15,7 @@ var log = u.Logger("path")
 // Resolver provides path resolution to IPFS
 // It has a pointer to a DAGService, which is uses to resolve nodes.
 type Resolver struct {
-	DAG *merkledag.DAGService
+	DAG merkledag.DAGService
 }
 
 // ResolvePath fetches the node for given path. It uses the first
diff --git a/pin/pin.go b/pin/pin.go
index b9c509a0343..a3f0e260b6e 100644
--- a/pin/pin.go
+++ b/pin/pin.go
@@ -32,11 +32,11 @@ type pinner struct {
 	recursePin set.BlockSet
 	directPin  set.BlockSet
 	indirPin   *indirectPin
-	dserv      *mdag.DAGService
+	dserv      mdag.DAGService
 	dstore     ds.Datastore
 }
 
-func NewPinner(dstore ds.Datastore, serv *mdag.DAGService) Pinner {
+func NewPinner(dstore ds.Datastore, serv mdag.DAGService) Pinner {
 
 	// Load set from given datastore...
 	rcds := nsds.Wrap(dstore, recursePinDatastoreKey)
@@ -151,7 +151,7 @@ func (p *pinner) IsPinned(key util.Key) bool {
 		p.indirPin.HasKey(key)
 }
 
-func LoadPinner(d ds.Datastore, dserv *mdag.DAGService) (Pinner, error) {
+func LoadPinner(d ds.Datastore, dserv mdag.DAGService) (Pinner, error) {
 	p := new(pinner)
 
 	{ // load recursive set
diff --git a/pin/pin_test.go b/pin/pin_test.go
index 8f6f6c343b1..7bf0756df56 100644
--- a/pin/pin_test.go
+++ b/pin/pin_test.go
@@ -24,7 +24,7 @@ func TestPinnerBasic(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	dserv := &mdag.DAGService{Blocks: bserv}
+	dserv := mdag.NewDAGService(bserv)
 
 	p := NewPinner(dstore, dserv)
 
diff --git a/unixfs/io/dagmodifier.go b/unixfs/io/dagmodifier.go
index 2d5fb77d924..ebec24cfce8 100644
--- a/unixfs/io/dagmodifier.go
+++ b/unixfs/io/dagmodifier.go
@@ -17,14 +17,14 @@ import (
 // perform surgery on a DAG 'file'
 // Dear god, please rename this to something more pleasant
 type DagModifier struct {
-	dagserv *mdag.DAGService
+	dagserv mdag.DAGService
 	curNode *mdag.Node
 
 	pbdata   *ftpb.Data
 	splitter chunk.BlockSplitter
 }
 
-func NewDagModifier(from *mdag.Node, serv *mdag.DAGService, spl chunk.BlockSplitter) (*DagModifier, error) {
+func NewDagModifier(from *mdag.Node, serv mdag.DAGService, spl chunk.BlockSplitter) (*DagModifier, error) {
 	pbd, err := ft.FromBytes(from.Data)
 	if err != nil {
 		return nil, err
diff --git a/unixfs/io/dagmodifier_test.go b/unixfs/io/dagmodifier_test.go
index 3686ff859ae..d45559b3adb 100644
--- a/unixfs/io/dagmodifier_test.go
+++ b/unixfs/io/dagmodifier_test.go
@@ -16,17 +16,17 @@ import (
 	logging "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-logging"
 )
 
-func getMockDagServ(t *testing.T) *mdag.DAGService {
+func getMockDagServ(t *testing.T) mdag.DAGService {
 	dstore := ds.NewMapDatastore()
 	bserv, err := bs.NewBlockService(dstore, nil)
 	if err != nil {
 		t.Fatal(err)
 	}
-	return &mdag.DAGService{Blocks: bserv}
+	return mdag.NewDAGService(bserv)
 }
 
-func getNode(t *testing.T, dserv *mdag.DAGService, size int64) ([]byte, *mdag.Node) {
-	dw := NewDagWriter(dserv, &chunk.SizeSplitter{Size: 500})
+func getNode(t *testing.T, dserv mdag.DAGService, size int64) ([]byte, *mdag.Node) {
+	dw := NewDagWriter(dserv, &chunk.SizeSplitter{500})
 
 	n, err := io.CopyN(dw, u.NewFastRand(), size)
 	if err != nil {
@@ -36,7 +36,11 @@ func getNode(t *testing.T, dserv *mdag.DAGService, size int64) ([]byte, *mdag.No
 		t.Fatal("Incorrect copy amount!")
 	}
 
-	dw.Close()
+	err = dw.Close()
+	if err != nil {
+		t.Fatal("DagWriter failed to close,", err)
+	}
+
 	node := dw.GetNode()
 
 	dr, err := NewDagReader(node, dserv)
diff --git a/unixfs/io/dagreader.go b/unixfs/io/dagreader.go
index 84691610377..17ad8737193 100644
--- a/unixfs/io/dagreader.go
+++ b/unixfs/io/dagreader.go
@@ -16,7 +16,7 @@ var ErrIsDir = errors.New("this dag node is a directory")
 
 // DagReader provides a way to easily read the data contained in a dag.
 type DagReader struct {
-	serv     *mdag.DAGService
+	serv     mdag.DAGService
 	node     *mdag.Node
 	position int
 	buf      *bytes.Buffer
@@ -24,7 +24,7 @@ type DagReader struct {
 
 // NewDagReader creates a new reader object that reads the data represented by the given
 // node, using the passed in DAGService for data retreival
-func NewDagReader(n *mdag.Node, serv *mdag.DAGService) (io.Reader, error) {
+func NewDagReader(n *mdag.Node, serv mdag.DAGService) (io.Reader, error) {
 	pb := new(ftpb.Data)
 	err := proto.Unmarshal(n.Data, pb)
 	if err != nil {
diff --git a/unixfs/io/dagwriter.go b/unixfs/io/dagwriter.go
index 4abb1b36c76..c9b91cc589a 100644
--- a/unixfs/io/dagwriter.go
+++ b/unixfs/io/dagwriter.go
@@ -10,7 +10,7 @@ import (
 var log = util.Logger("dagwriter")
 
 type DagWriter struct {
-	dagserv   *dag.DAGService
+	dagserv   dag.DAGService
 	node      *dag.Node
 	totalSize int64
 	splChan   chan []byte
@@ -19,7 +19,7 @@ type DagWriter struct {
 	seterr    error
 }
 
-func NewDagWriter(ds *dag.DAGService, splitter chunk.BlockSplitter) *DagWriter {
+func NewDagWriter(ds dag.DAGService, splitter chunk.BlockSplitter) *DagWriter {
 	dw := new(DagWriter)
 	dw.dagserv = ds
 	dw.splChan = make(chan []byte, 8)
diff --git a/unixfs/io/dagwriter_test.go b/unixfs/io/dagwriter_test.go
index d0b8f45d16f..08779e2c1f2 100644
--- a/unixfs/io/dagwriter_test.go
+++ b/unixfs/io/dagwriter_test.go
@@ -7,6 +7,7 @@ import (
 
 	ds "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore"
 	bs "github.com/jbenet/go-ipfs/blockservice"
+	"github.com/jbenet/go-ipfs/importer"
 	chunk "github.com/jbenet/go-ipfs/importer/chunk"
 	mdag "github.com/jbenet/go-ipfs/merkledag"
 )
@@ -53,7 +54,7 @@ func TestDagWriter(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	dag := &mdag.DAGService{Blocks: bserv}
+	dag := mdag.NewDAGService(bserv)
 	dw := NewDagWriter(dag, &chunk.SizeSplitter{Size: 4096})
 
 	nbytes := int64(1024 * 1024 * 2)
@@ -87,7 +88,7 @@ func TestMassiveWrite(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	dag := &mdag.DAGService{Blocks: bserv}
+	dag := mdag.NewDAGService(bserv)
 	dw := NewDagWriter(dag, &chunk.SizeSplitter{Size: 4096})
 
 	nbytes := int64(1024 * 1024 * 1024 * 16)
@@ -107,7 +108,7 @@ func BenchmarkDagWriter(b *testing.B) {
 	if err != nil {
 		b.Fatal(err)
 	}
-	dag := &mdag.DAGService{Blocks: bserv}
+	dag := mdag.NewDAGService(bserv)
 
 	b.ResetTimer()
 	nbytes := int64(100000)
@@ -125,3 +126,45 @@ func BenchmarkDagWriter(b *testing.B) {
 	}
 
 }
+
+func TestAgainstImporter(t *testing.T) {
+	dstore := ds.NewMapDatastore()
+	bserv, err := bs.NewBlockService(dstore, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	dag := mdag.NewDAGService(bserv)
+
+	nbytes := int64(1024 * 1024 * 2)
+
+	// DagWriter
+	dw := NewDagWriter(dag, &chunk.SizeSplitter{4096})
+	n, err := io.CopyN(dw, &datasource{}, nbytes)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if n != nbytes {
+		t.Fatal("Copied incorrect amount of bytes!")
+	}
+
+	dw.Close()
+	dwNode := dw.GetNode()
+	dwKey, err := dwNode.Key()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// DagFromFile
+	rl := &io.LimitedReader{&datasource{}, nbytes}
+
+	dffNode, err := importer.NewDagFromReaderWithSplitter(rl, &chunk.SizeSplitter{4096})
+	dffKey, err := dffNode.Key()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if dwKey.String() != dffKey.String() {
+		t.Errorf("\nDagWriter produced     %s\n"+
+			"DagFromReader produced %s",
+			dwKey, dffKey)
+	}
+}