diff --git a/graphsync.go b/graphsync.go
index 17f2dc07..e0fb6fc7 100644
--- a/graphsync.go
+++ b/graphsync.go
@@ -175,6 +175,9 @@ type BlockData interface {
 
 	// BlockSize specifies the amount of data actually transmitted over the network
 	BlockSizeOnWire() uint64
+
+	// The index of this block in the selector traversal
+	Index() int64
 }
 
 // IncomingRequestHookActions are actions that a request hook can take to change
diff --git a/impl/graphsync_test.go b/impl/graphsync_test.go
index 1ec45dce..5f9a6bdb 100644
--- a/impl/graphsync_test.go
+++ b/impl/graphsync_test.go
@@ -316,7 +316,7 @@ func TestGraphsyncRoundTripIgnoreCids(t *testing.T) {
 	totalSent := 0
 	totalSentOnWire := 0
 	responder.RegisterOutgoingBlockHook(func(p peer.ID, requestData graphsync.RequestData, blockData graphsync.BlockData, hookActions graphsync.OutgoingBlockHookActions) {
-		totalSent++
+		totalSent = int(blockData.Index())
 		if blockData.BlockSizeOnWire() > 0 {
 			totalSentOnWire++
 		}
@@ -364,8 +364,11 @@ func TestGraphsyncRoundTripIgnoreNBlocks(t *testing.T) {
 	totalSent := 0
 	totalSentOnWire := 0
 	responder.RegisterOutgoingBlockHook(func(p peer.ID, requestData graphsync.RequestData, blockData graphsync.BlockData, hookActions graphsync.OutgoingBlockHookActions) {
-		totalSent++
-		if blockData.BlockSizeOnWire() > 0 {
+		totalSent = int(blockData.Index())
+		if blockData.Index() <= 50 {
+			require.True(t, blockData.BlockSizeOnWire() == 0)
+		} else {
+			require.True(t, blockData.BlockSizeOnWire() > 0)
 			totalSentOnWire++
 		}
 	})
diff --git a/requestmanager/executor/executor.go b/requestmanager/executor/executor.go
index 3158004a..253fd06f 100644
--- a/requestmanager/executor/executor.go
+++ b/requestmanager/executor/executor.go
@@ -190,7 +190,7 @@ func (e *Executor) advanceTraversal(rt RequestTask, result types.AsyncLoadResult
 }
 
 func (e *Executor) processResult(rt RequestTask, link ipld.Link, result types.AsyncLoadResult) error {
-	err := e.onNewBlock(rt, &blockData{link, result.Local, uint64(len(result.Data))})
+	err := e.onNewBlock(rt, &blockData{link, result.Local, uint64(len(result.Data)), int64(rt.Traverser.NBlocksTraversed())})
 	select {
 	case <-rt.PauseMessages:
 		if err == nil {
@@ -243,6 +243,7 @@ type blockData struct {
 	link  ipld.Link
 	local bool
 	size  uint64
+	index int64
 }
 
 // Link is the link/cid for the block
@@ -262,3 +263,7 @@ func (bd *blockData) BlockSizeOnWire() uint64 {
 	}
 	return bd.size
 }
+
+func (bd *blockData) Index() int64 {
+	return bd.index
+}
diff --git a/responsemanager/responseassembler/peerlinktracker.go b/responsemanager/responseassembler/peerlinktracker.go
index 3bea04c3..b41e5784 100644
--- a/responsemanager/responseassembler/peerlinktracker.go
+++ b/responsemanager/responseassembler/peerlinktracker.go
@@ -91,7 +91,7 @@ func (prs *peerLinkTracker) FinishTracking(requestID graphsync.RequestID) bool {
 
 // RecordLinkTraversal records whether a link is found for a request.
 func (prs *peerLinkTracker) RecordLinkTraversal(requestID graphsync.RequestID,
-	link ipld.Link, hasBlock bool) bool {
+	link ipld.Link, hasBlock bool) (bool, int64) {
 	prs.linkTrackerLk.Lock()
 	defer prs.linkTrackerLk.Unlock()
 	prs.blockSentCount[requestID]++
@@ -99,5 +99,5 @@ func (prs *peerLinkTracker) RecordLinkTraversal(requestID graphsync.RequestID,
 	linkTracker := prs.getLinkTracker(requestID)
 	isUnique := linkTracker.BlockRefCount(link) == 0
 	linkTracker.RecordLinkTraversal(requestID, link, hasBlock)
-	return hasBlock && notSkipped && isUnique
+	return hasBlock && notSkipped && isUnique, prs.blockSentCount[requestID]
 }
diff --git a/responsemanager/responseassembler/responseBuilder.go b/responsemanager/responseassembler/responseBuilder.go
index 7752813c..1b78d8b8 100644
--- a/responsemanager/responseassembler/responseBuilder.go
+++ b/responsemanager/responseassembler/responseBuilder.go
@@ -60,9 +60,9 @@ func (rb *responseBuilder) AddNotifee(notifee notifications.Notifee) {
 func (rb *responseBuilder) setupBlockOperation(
 	link ipld.Link, data []byte) blockOperation {
 	hasBlock := data != nil
-	send := rb.linkTracker.RecordLinkTraversal(rb.requestID, link, hasBlock)
+	send, index := rb.linkTracker.RecordLinkTraversal(rb.requestID, link, hasBlock)
 	return blockOperation{
-		data, send, link, rb.requestID,
+		data, send, link, rb.requestID, index,
 	}
 }
 
@@ -113,6 +113,7 @@ type blockOperation struct {
 	sendBlock bool
 	link      ipld.Link
 	requestID graphsync.RequestID
+	index     int64
 }
 
 func (bo blockOperation) build(builder *gsmsg.Builder) {
@@ -142,6 +143,10 @@ func (bo blockOperation) BlockSizeOnWire() uint64 {
 	return bo.BlockSize()
 }
 
+func (bo blockOperation) Index() int64 {
+	return bo.index
+}
+
 func (bo blockOperation) size() uint64 {
 	return bo.BlockSizeOnWire()
 }
diff --git a/responsemanager/responsemanager_test.go b/responsemanager/responsemanager_test.go
index ef5267f1..dd5f71e7 100644
--- a/responsemanager/responsemanager_test.go
+++ b/responsemanager/responsemanager_test.go
@@ -884,6 +884,10 @@ func (fbd fakeBlkData) BlockSizeOnWire() uint64 {
 	return fbd.size
 }
 
+func (fbd fakeBlkData) Index() int64 {
+	return 0
+}
+
 func (fra *fakeResponseAssembler) sendResponse(
 	requestID graphsync.RequestID,
 	link ipld.Link,
diff --git a/testutil/testutil.go b/testutil/testutil.go
index d9b0e978..fd8b3149 100644
--- a/testutil/testutil.go
+++ b/testutil/testutil.go
@@ -229,8 +229,9 @@ func NewTestLink() ipld.Link {
 }
 
 type fakeBlkData struct {
-	link ipld.Link
-	size uint64
+	link  ipld.Link
+	size  uint64
+	index int64
 }
 
 func (fbd fakeBlkData) Link() ipld.Link {
@@ -245,10 +246,15 @@ func (fbd fakeBlkData) BlockSizeOnWire() uint64 {
 	return fbd.size
 }
 
+func (fbd fakeBlkData) Index() int64 {
+	return fbd.index
+}
+
 // NewFakeBlockData returns a fake block that matches the block data interface
 func NewFakeBlockData() graphsync.BlockData {
 	return &fakeBlkData{
-		link: cidlink.Link{Cid: GenerateCids(1)[0]},
-		size: rand.Uint64(),
+		link:  cidlink.Link{Cid: GenerateCids(1)[0]},
+		size:  rand.Uint64(),
+		index: rand.Int63(),
 	}
 }