.gitignore                        | 1 +
 client.go                         | 2 +-
 file.go                           | 2 +-
 file_test.go                      | 2 +-
 go.mod                            | 3 ++-
 go.sum                            | 6 ++++--
 internal/request-strategy/peer.go | 2 ++
 misc.go                           | 2 +-
 ordered-bitmap.go                 | 4 ++++
 peer-impl.go                      | 2 +-
 peer.go                           | 2 +-
 peerconn.go                       | 2 +-
 piece.go                          | 3 +--
 requesting.go                     | 2 +-
 roaring.go                        | 9 +++------
 torrent-piece-request-order.go    | 2 +-
 torrent.go                        | 2 +-
 typed-roaring/bitmap.go           | 8 ++++++--
 typed-roaring/iterator.go         | 2 +-
 webseed-peer.go                   | 6 +++---
 webseed/client.go                 | 2 +-

diff --git a/.gitignore b/.gitignore
index aaa3ebc23096440095c7740a83e053231ecb4ebc..296db6a902cde700cba1d87bc0d63a7b7b0acfb8 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,3 +2,4 @@ .idea
 *-run.gob
 .envrc*
 .DS_Store
+/vendor
\ No newline at end of file
diff --git a/client.go b/client.go
index c35df32fb125bb55de3955756149f228f6d1a1aa..fbc8c8264458504f389649e72298caaa36360c07 100644
--- a/client.go
+++ b/client.go
@@ -21,7 +21,7 @@ 	"slices"
 	"strconv"
 	"time"
 
-	"github.com/RoaringBitmap/roaring"
+	"github.com/RoaringBitmap/roaring/v2"
 	"github.com/anacrolix/chansync"
 	"github.com/anacrolix/chansync/events"
 	"github.com/anacrolix/dht/v2"
diff --git a/file.go b/file.go
index be2c64ac83c9b5a985678e213b2afc598a6ecd20..abf4070441023a046d1523037636f700e623ec02 100644
--- a/file.go
+++ b/file.go
@@ -3,7 +3,7 @@
 import (
 	"iter"
 
-	"github.com/RoaringBitmap/roaring"
+	"github.com/RoaringBitmap/roaring/v2"
 	g "github.com/anacrolix/generics"
 	"github.com/anacrolix/missinggo/v2/bitmap"
 
diff --git a/file_test.go b/file_test.go
index 2f57bcf46ae3d747f499598eeb1116dcb2015df7..0d594ec073f598e2802be749159810aecdda878b 100644
--- a/file_test.go
+++ b/file_test.go
@@ -3,7 +3,7 @@
 import (
 	"testing"
 
-	"github.com/RoaringBitmap/roaring"
+	"github.com/RoaringBitmap/roaring/v2"
 	"github.com/stretchr/testify/assert"
 )
 
diff --git a/go.mod b/go.mod
index 2e23caf6398d0343d163b086ad2a023770b5aa77..3d087e2fef441d15c0a71155750e91b295f18f57 100644
--- a/go.mod
+++ b/go.mod
@@ -4,6 +4,7 @@ go 1.24.0
 
 require (
 	github.com/RoaringBitmap/roaring v1.2.3
+	github.com/RoaringBitmap/roaring/v2 v2.15.0
 	github.com/alexflint/go-arg v1.4.3
 	github.com/anacrolix/bargle v1.0.0
 	github.com/anacrolix/bargle/v2 v2.0.0
@@ -68,7 +69,7 @@ 	github.com/anacrolix/mmsg v1.0.1 // indirect
 	github.com/anacrolix/stm v0.5.0 // indirect
 	github.com/benbjohnson/immutable v0.4.1-0.20221220213129-8932b999621d // indirect
 	github.com/beorn7/perks v1.0.1 // indirect
-	github.com/bits-and-blooms/bitset v1.2.2 // indirect
+	github.com/bits-and-blooms/bitset v1.24.2 // indirect
 	github.com/cenkalti/backoff/v5 v5.0.3 // indirect
 	github.com/cespare/xxhash/v2 v2.3.0 // indirect
 	github.com/ebitengine/purego v0.9.1 // indirect
diff --git a/go.sum b/go.sum
index 26244c13ea0a410b6627b282ef77e41bb704c0f8..5ea651437b9feb9040c5e43894a5d100b3b8d59e 100644
--- a/go.sum
+++ b/go.sum
@@ -44,6 +44,8 @@ github.com/RoaringBitmap/roaring v0.4.17/go.mod h1:D3qVegWTmfCaX4Bl5CrBE9hfrSrrXIr8KVNvRsDi1NI=
 github.com/RoaringBitmap/roaring v0.4.23/go.mod h1:D0gp8kJQgE1A4LQ5wFLggQEyvDi06Mq5mKs52e1TwOo=
 github.com/RoaringBitmap/roaring v1.2.3 h1:yqreLINqIrX22ErkKI0vY47/ivtJr6n+kMhVOVmhWBY=
 github.com/RoaringBitmap/roaring v1.2.3/go.mod h1:plvDsJQpxOC5bw8LRteu/MLWHsHez/3y6cubLI4/1yE=
+github.com/RoaringBitmap/roaring/v2 v2.15.0 h1:gCbixa3UiG7g6WUZNVOfEEg2HTc1vR4OVdMkX8t1ZFc=
+github.com/RoaringBitmap/roaring/v2 v2.15.0/go.mod h1:eq4wdNXxtJIS/oikeCzdX1rBzek7ANzbth041hrU8Q4=
 github.com/Shopify/sarama v1.19.0/go.mod h1:FVkBWblsNy7DGZRfXLU0O9RCGt5g3g3yEuWXgklEdEo=
 github.com/Shopify/toxiproxy v2.1.4+incompatible/go.mod h1:OXgGpZ6Cli1/URJOF1DMxUHB2q5Ap20/P/eIdh4G0pI=
 github.com/ajwerner/btree v0.0.0-20211221152037-f427b3e689c0 h1:byYvvbfSo3+9efR4IeReh77gVs4PnNDR3AMOE9NJ7a0=
@@ -143,8 +145,8 @@ github.com/beorn7/perks v1.0.0/go.mod h1:KWe93zE9D1o94FZ5RNwFwVgaQK1VOXiVxmqh+CedLV8=
 github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
 github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
 github.com/bits-and-blooms/bitset v1.2.0/go.mod h1:gIdJ4wp64HaoK2YrL1Q5/N7Y16edYb8uY+O0FJTyyDA=
-github.com/bits-and-blooms/bitset v1.2.2 h1:J5gbX05GpMdBjCvQ9MteIg2KKDExr7DrgK+Yc15FvIk=
-github.com/bits-and-blooms/bitset v1.2.2/go.mod h1:gIdJ4wp64HaoK2YrL1Q5/N7Y16edYb8uY+O0FJTyyDA=
+github.com/bits-and-blooms/bitset v1.24.2 h1:M7/NzVbsytmtfHbumG+K2bremQPMJuqv1JD3vOaFxp0=
+github.com/bits-and-blooms/bitset v1.24.2/go.mod h1:7hO7Gc7Pp1vODcmWvKMRA9BNmbv6a/7QIWpPxHddWR8=
 github.com/bradfitz/iter v0.0.0-20140124041915-454541ec3da2/go.mod h1:PyRFw1Lt2wKX4ZVSQ2mk+PeDa1rxyObEDlApuIsUKuo=
 github.com/bradfitz/iter v0.0.0-20190303215204-33e6a9893b0c/go.mod h1:PyRFw1Lt2wKX4ZVSQ2mk+PeDa1rxyObEDlApuIsUKuo=
 github.com/bradfitz/iter v0.0.0-20191230175014-e8f45d346db8 h1:GKTyiRCL6zVf5wWaqKnf+7Qs6GbEPfd4iMOitWzXJx8=
diff --git a/internal/request-strategy/peer.go b/internal/request-strategy/peer.go
index 1eea0329ebf6148916da7e41c169112f409c59f5..72b0972465dadfc4435cbbd6be32e1cf9e741e80 100644
--- a/internal/request-strategy/peer.go
+++ b/internal/request-strategy/peer.go
@@ -33,4 +33,6 @@ 	// See roaring.Bitmap.CheckedRemove.
 	CheckedRemove(RequestIndex) bool
 	// Iterate a snapshot of the values. It is safe to mutate the underlying data structure.
 	IterateSnapshot(func(RequestIndex) bool)
+
+	RangeCardinality(start, end RequestIndex) uint64
 }
diff --git a/misc.go b/misc.go
index 511d6d3e6dd223526db62a0e64954a4f8b684f7f..94b3187bb2d8cf95ef3cf9e895905798bf1424e5 100644
--- a/misc.go
+++ b/misc.go
@@ -4,7 +4,7 @@ import (
 	"errors"
 	"net"
 
-	"github.com/RoaringBitmap/roaring"
+	"github.com/RoaringBitmap/roaring/v2"
 	"github.com/anacrolix/missinggo/v2"
 	"github.com/anacrolix/missinggo/v2/panicif"
 	"golang.org/x/time/rate"
diff --git a/ordered-bitmap.go b/ordered-bitmap.go
index 849a1380b2f6e59e36f096b33c83224ddadbfe0a..f304f97c716f71f6f74a9c92d4b7502f30904ff8 100644
--- a/ordered-bitmap.go
+++ b/ordered-bitmap.go
@@ -72,3 +72,7 @@ 	o.order.Remove(o.elements[index])
 	delete(o.elements, index)
 	return true
 }
+
+func (o *orderedBitmap[T]) RangeCardinality(start, end T) uint64 {
+	return o.bitmap.RangeCardinality(start, end)
+}
\ No newline at end of file
diff --git a/peer-impl.go b/peer-impl.go
index 25fe5a72b9591e5ca09938146ef01c9b352ac277..cb31a817f067e3945a4a28880df985a50d1d5549 100644
--- a/peer-impl.go
+++ b/peer-impl.go
@@ -3,7 +3,7 @@
 import (
 	"io"
 
-	"github.com/RoaringBitmap/roaring"
+	"github.com/RoaringBitmap/roaring/v2"
 
 	"github.com/anacrolix/torrent/metainfo"
 	pp "github.com/anacrolix/torrent/peer_protocol"
diff --git a/peer.go b/peer.go
index 0902938f95118c7360b402209d6bca527866708b..9a5ae4fd3bd11030e644a586daf49107aa6bc2ab 100644
--- a/peer.go
+++ b/peer.go
@@ -11,7 +11,7 @@ 	"strings"
 	"sync"
 	"time"
 
-	"github.com/RoaringBitmap/roaring"
+	"github.com/RoaringBitmap/roaring/v2"
 	"github.com/anacrolix/chansync"
 	g "github.com/anacrolix/generics"
 	"github.com/anacrolix/log"
diff --git a/peerconn.go b/peerconn.go
index 9444428ecab9cebf5c7262f6127b4af64fb42f3f..d7418edbdf152981b550f6d6625c0336dcb0abd6 100644
--- a/peerconn.go
+++ b/peerconn.go
@@ -16,7 +16,7 @@ 	"sync/atomic"
 	"time"
 	"weak"
 
-	"github.com/RoaringBitmap/roaring"
+	"github.com/RoaringBitmap/roaring/v2"
 	"github.com/anacrolix/chansync"
 	g "github.com/anacrolix/generics"
 	"github.com/anacrolix/log"
diff --git a/piece.go b/piece.go
index bab0dd7b70778b240994f214da18c34bc8ba9594..1252e205ecf3ba6b92a6f32c34f482362af1cc2a 100644
--- a/piece.go
+++ b/piece.go
@@ -7,7 +7,7 @@ 	"fmt"
 	"iter"
 	"sync"
 
-	"github.com/RoaringBitmap/roaring"
+	"github.com/RoaringBitmap/roaring/v2"
 	"github.com/anacrolix/chansync"
 	g "github.com/anacrolix/generics"
 	"github.com/anacrolix/missinggo/v2/bitmap"
@@ -462,4 +462,3 @@ 			cur,
 		})
 	}
 }
-
diff --git a/requesting.go b/requesting.go
index 155f597ba983e9392278ea19878612c295750743..b903739dbead5d8296945a8e01dad57f8f036b1b 100644
--- a/requesting.go
+++ b/requesting.go
@@ -10,7 +10,7 @@ 	"runtime/pprof"
 	"time"
 	"unsafe"
 
-	"github.com/RoaringBitmap/roaring"
+	"github.com/RoaringBitmap/roaring/v2"
 	g "github.com/anacrolix/generics"
 	"github.com/anacrolix/generics/heap"
 	"github.com/anacrolix/multiless"
diff --git a/roaring.go b/roaring.go
index f8e622b1163072364650d041598aa2eb39a1348a..e75ba99560787cf4c6e637132142104a9e7f3211 100644
--- a/roaring.go
+++ b/roaring.go
@@ -5,10 +5,7 @@
 // Return the number of bits set in the range. To do this we need the rank of the item before the
 // first, and the rank of the last item. An off-by-one minefield. Hopefully I haven't missed
 // something in roaring's API that provides this.
-func roaringBitmapRangeCardinality[T typedRoaring.BitConstraint](bm interface{ Rank(T) uint64 }, start, end T) (card uint64) {
-	card = bm.Rank(end - 1)
-	if start != 0 {
-		card -= bm.Rank(start - 1)
-	}
+func roaringBitmapRangeCardinality[T typedRoaring.BitConstraint](bm interface{ RangeCardinality(T, T) uint64 }, start, end T) (card uint64) {
+	card = bm.RangeCardinality(start, end)
 	return
-}
+} 
diff --git a/torrent-piece-request-order.go b/torrent-piece-request-order.go
index cedc919d4f6933d6d4dc7bf28e401b64b9043b91..f3b8da98fe59ce9cae669aba9676927f2f755de3 100644
--- a/torrent-piece-request-order.go
+++ b/torrent-piece-request-order.go
@@ -3,7 +3,7 @@
 import (
 	"fmt"
 
-	"github.com/RoaringBitmap/roaring"
+	"github.com/RoaringBitmap/roaring/v2"
 	g "github.com/anacrolix/generics"
 	"github.com/anacrolix/torrent/internal/amortize"
 	requestStrategy "github.com/anacrolix/torrent/internal/request-strategy"
diff --git a/torrent.go b/torrent.go
index 76b164e0cad137945dae461e09b455dc783f9368..73ef35eafbf1f426b22add23e847260c19e26d21 100644
--- a/torrent.go
+++ b/torrent.go
@@ -25,7 +25,7 @@ 	"unique"
 	"unsafe"
 	"weak"
 
-	"github.com/RoaringBitmap/roaring"
+	"github.com/RoaringBitmap/roaring/v2"
 	"github.com/anacrolix/chansync"
 	"github.com/anacrolix/chansync/events"
 	"github.com/anacrolix/dht/v2"
diff --git a/typed-roaring/bitmap.go b/typed-roaring/bitmap.go
index d61ffe4864b4af24d5a5d016d2a7fc9461262fe8..2ce01f9e5288a5a0b6d865fa53e3c40972cce1b3 100644
--- a/typed-roaring/bitmap.go
+++ b/typed-roaring/bitmap.go
@@ -1,12 +1,12 @@
 package typedRoaring
 
 import (
-	"github.com/RoaringBitmap/roaring"
+	roaringv2 "github.com/RoaringBitmap/roaring/v2"
 )
 
 // TODO: Update to roaring v2 or higher
 type Bitmap[T BitConstraint] struct {
-	roaring.Bitmap
+	roaringv2.Bitmap
 }
 
 func (me *Bitmap[T]) Contains(x T) bool {
@@ -46,6 +46,10 @@
 // Returns an uninitialized iterator for the type of the receiver.
 func (Bitmap[T]) IteratorType() Iterator[T] {
 	return Iterator[T]{}
+}
+
+func (me Bitmap[T]) RangeCardinality(start, end T) uint64 {
+	return me.Bitmap.CardinalityInRange(uint64(start), uint64(end))
 }
 
 // TODO: Override Bitmap.Iterator.
diff --git a/typed-roaring/iterator.go b/typed-roaring/iterator.go
index 8766db1750d6aa8d8fb86b67a3d4e96d206c6f90..ab55c4eed34b7aab19b0e5f5c6465441d7e32df1 100644
--- a/typed-roaring/iterator.go
+++ b/typed-roaring/iterator.go
@@ -1,7 +1,7 @@
 package typedRoaring
 
 import (
-	"github.com/RoaringBitmap/roaring"
+	"github.com/RoaringBitmap/roaring/v2"
 )
 
 type Iterator[T BitConstraint] struct {
diff --git a/webseed-peer.go b/webseed-peer.go
index 0acd585f98d09a699155812423a3bfc10a4524b7..222679fde18ccf71ce01859d40fe38637b91829f 100644
--- a/webseed-peer.go
+++ b/webseed-peer.go
@@ -14,7 +14,7 @@ 	"sync"
 	"syscall"
 	"time"
 
-	"github.com/RoaringBitmap/roaring"
+	"github.com/RoaringBitmap/roaring/v2"
 	g "github.com/anacrolix/generics"
 	"github.com/anacrolix/missinggo/v2/panicif"
 	"golang.org/x/net/http2"
@@ -26,8 +26,8 @@ )
 
 type webseedPeer struct {
 	// First field for stats alignment.
-	peer   Peer
-	client webseed.Client
+	peer           Peer
+	client         webseed.Client
 	activeRequests map[*webseedRequest]struct{}
 	locker         sync.Locker
 	hostKey        webseedHostKeyHandle
diff --git a/webseed/client.go b/webseed/client.go
index accfb273b4b11ee0280109b978d2874ff7240866..4f7c32206775fa78ae08cbf62d7f13827915f2c3 100644
--- a/webseed/client.go
+++ b/webseed/client.go
@@ -12,7 +12,7 @@ 	"runtime/pprof"
 	"strings"
 	"sync"
 
-	"github.com/RoaringBitmap/roaring"
+	"github.com/RoaringBitmap/roaring/v2"
 	g "github.com/anacrolix/generics"
 	"github.com/anacrolix/missinggo/v2/panicif"
 	"github.com/dustin/go-humanize"