diff --git a/go.mod b/go.mod
index 6ec675ed4..f707d7c93 100644
--- a/go.mod
+++ b/go.mod
@@ -17,7 +17,7 @@ require (
 	github.com/matrix-org/go-http-js-libp2p v0.0.0-20200318135427-31631a9ef51f
 	github.com/matrix-org/go-sqlite3-js v0.0.0-20200325174927-327088cdef10
 	github.com/matrix-org/gomatrix v0.0.0-20190528120928-7df988a63f26
-	github.com/matrix-org/gomatrixserverlib v0.0.0-20200423090438-562549dbe799
+	github.com/matrix-org/gomatrixserverlib v0.0.0-20200424154222-2827b39252bd
 	github.com/matrix-org/naffka v0.0.0-20200422140631-181f1ee7401f
 	github.com/matrix-org/util v0.0.0-20190711121626-527ce5ddefc7
 	github.com/mattn/go-sqlite3 v2.0.2+incompatible
diff --git a/go.sum b/go.sum
index 016b6c128..6ead661ed 100644
--- a/go.sum
+++ b/go.sum
@@ -371,6 +371,8 @@ github.com/matrix-org/gomatrixserverlib v0.0.0-20200422082552-d7b4202c47f3 h1:xi
 github.com/matrix-org/gomatrixserverlib v0.0.0-20200422082552-d7b4202c47f3/go.mod h1:JsAzE1Ll3+gDWS9JSUHPJiiyAksvOOnGWF2nXdg4ZzU=
 github.com/matrix-org/gomatrixserverlib v0.0.0-20200423090438-562549dbe799 h1:OsoUMTirIpeuZJdYkKKiYe6jm0E5viZR7aOS9K465QI=
 github.com/matrix-org/gomatrixserverlib v0.0.0-20200423090438-562549dbe799/go.mod h1:JsAzE1Ll3+gDWS9JSUHPJiiyAksvOOnGWF2nXdg4ZzU=
+github.com/matrix-org/gomatrixserverlib v0.0.0-20200424154222-2827b39252bd h1:243fMfK0XqTQsdUY3IIqtxPX5g9MfPTaAP92CseqOek=
+github.com/matrix-org/gomatrixserverlib v0.0.0-20200424154222-2827b39252bd/go.mod h1:JsAzE1Ll3+gDWS9JSUHPJiiyAksvOOnGWF2nXdg4ZzU=
 github.com/matrix-org/naffka v0.0.0-20200127221512-0716baaabaf1 h1:osLoFdOy+ChQqVUn2PeTDETFftVkl4w9t/OW18g3lnk=
 github.com/matrix-org/naffka v0.0.0-20200127221512-0716baaabaf1/go.mod h1:cXoYQIENbdWIQHt1SyCo6Bl3C3raHwJ0wgVrXHSqf+A=
 github.com/matrix-org/naffka v0.0.0-20200422140631-181f1ee7401f h1:pRz4VTiRCO4zPlEMc3ESdUOcW4PXHH4Kj+YDz1XyE+Y=
diff --git a/roomserver/query/backfill.go b/roomserver/query/backfill.go
index 5614d9450..45bf5b593 100644
--- a/roomserver/query/backfill.go
+++ b/roomserver/query/backfill.go
@@ -14,6 +14,30 @@ type backfillRequester struct {
 	db         storage.Database
 	fedClient  *gomatrixserverlib.FederationClient
 	thisServer gomatrixserverlib.ServerName
+
+	// per-request state
+	servers  []gomatrixserverlib.ServerName
+	stateIDs []string
+}
+
+func (b *backfillRequester) StateIDsBeforeEvent(ctx context.Context, roomID, atEventID string) ([]string, error) {
+	c := gomatrixserverlib.FederatedStateProvider{
+		FedClient:      b.fedClient,
+		AuthEventsOnly: true,
+		Server:         b.servers[0],
+	}
+	res, err := c.StateIDsAtEvent(ctx, roomID, atEventID)
+	b.stateIDs = res
+	return res, err
+}
+
+func (b *backfillRequester) StateBeforeEvent(ctx context.Context, roomVer gomatrixserverlib.RoomVersion, roomID, atEventID string, eventIDs []string) (map[string]*gomatrixserverlib.Event, error) {
+	c := gomatrixserverlib.FederatedStateProvider{
+		FedClient:      b.fedClient,
+		AuthEventsOnly: true,
+		Server:         b.servers[0],
+	}
+	return c.StateAtEvent(ctx, roomVer, roomID, atEventID, eventIDs)
 }
 
 // ServersAtEvent is called when trying to determine which server to request from.
@@ -49,6 +73,7 @@ func (b *backfillRequester) ServersAtEvent(ctx context.Context, roomID, eventID
 		}
 		servers = append(servers, server)
 	}
+	b.servers = servers
 	return
 }