diff --git a/roomserver/types/headered_event.go b/roomserver/types/headered_event.go
index 52d006bd9..783999822 100644
--- a/roomserver/types/headered_event.go
+++ b/roomserver/types/headered_event.go
@@ -18,6 +18,7 @@ import (
 	"unsafe"
 
 	"github.com/matrix-org/gomatrixserverlib"
+	"github.com/matrix-org/gomatrixserverlib/spec"
 )
 
 // HeaderedEvent is an Event which serialises to the headered form, which includes
@@ -25,6 +26,10 @@ import (
 type HeaderedEvent struct {
 	gomatrixserverlib.PDU
 	Visibility gomatrixserverlib.HistoryVisibility
+	// TODO: Remove this. This is a temporary workaround to store the userID in the syncAPI.
+	// 		It really should be the userKey instead.
+	UserID           spec.UserID
+	StateKeyResolved *string
 }
 
 func (h *HeaderedEvent) CacheCost() int {
diff --git a/syncapi/consumers/roomserver.go b/syncapi/consumers/roomserver.go
index d468dfc98..785676755 100644
--- a/syncapi/consumers/roomserver.go
+++ b/syncapi/consumers/roomserver.go
@@ -256,16 +256,19 @@ func (s *OutputRoomEventConsumer) onNewRoomEvent(
 		}
 	}
 
-	pduPos, err := s.db.WriteEvent(
-		ctx,
-		ev,
-		addsStateEvents,
-		msg.AddsStateEventIDs,
-		msg.RemovesStateEventIDs,
-		msg.TransactionID,
-		false,
-		msg.HistoryVisibility,
-	)
+	validRoomID, err := spec.NewRoomID(ev.RoomID())
+	if err != nil {
+		return err
+	}
+
+	userID, err := s.rsAPI.QueryUserIDForSender(ctx, *validRoomID, ev.SenderID())
+	if err != nil {
+		return err
+	}
+
+	ev.UserID = *userID
+
+	pduPos, err := s.db.WriteEvent(ctx, ev, addsStateEvents, msg.AddsStateEventIDs, msg.RemovesStateEventIDs, msg.TransactionID, false, msg.HistoryVisibility)
 	if err != nil {
 		// panic rather than continue with an inconsistent database
 		log.WithFields(log.Fields{
@@ -315,16 +318,19 @@ func (s *OutputRoomEventConsumer) onOldRoomEvent(
 	// hack but until we have some better strategy for dealing with
 	// old events in the sync API, this should at least prevent us
 	// from confusing clients into thinking they've joined/left rooms.
-	pduPos, err := s.db.WriteEvent(
-		ctx,
-		ev,
-		[]*rstypes.HeaderedEvent{},
-		[]string{},           // adds no state
-		[]string{},           // removes no state
-		nil,                  // no transaction
-		ev.StateKey() != nil, // exclude from sync?,
-		msg.HistoryVisibility,
-	)
+
+	validRoomID, err := spec.NewRoomID(ev.RoomID())
+	if err != nil {
+		return err
+	}
+
+	userID, err := s.rsAPI.QueryUserIDForSender(ctx, *validRoomID, ev.SenderID())
+	if err != nil {
+		return err
+	}
+	ev.UserID = *userID
+
+	pduPos, err := s.db.WriteEvent(ctx, ev, []*rstypes.HeaderedEvent{}, []string{}, []string{}, nil, ev.StateKey() != nil, msg.HistoryVisibility)
 	if err != nil {
 		// panic rather than continue with an inconsistent database
 		log.WithFields(log.Fields{
@@ -537,6 +543,7 @@ func (s *OutputRoomEventConsumer) onPurgeRoom(
 }
 
 func (s *OutputRoomEventConsumer) updateStateEvent(event *rstypes.HeaderedEvent) (*rstypes.HeaderedEvent, error) {
+	event.StateKeyResolved = event.StateKey()
 	if event.StateKey() == nil {
 		return event, nil
 	}
@@ -556,6 +563,28 @@ func (s *OutputRoomEventConsumer) updateStateEvent(event *rstypes.HeaderedEvent)
 		return event, err
 	}
 
+	validRoomID, err := spec.NewRoomID(event.RoomID())
+	if err != nil {
+		return event, err
+	}
+
+	if event.StateKey() != nil {
+		if *event.StateKey() != "" {
+			sku, err := s.rsAPI.QueryUserIDForSender(s.ctx, *validRoomID, spec.SenderID(stateKey))
+			if err == nil && sku != nil {
+				sKey := sku.String()
+				event.StateKeyResolved = &sKey
+			}
+		}
+	}
+
+	userID, err := s.rsAPI.QueryUserIDForSender(s.ctx, *validRoomID, event.SenderID())
+	if err != nil {
+		return event, err
+	}
+
+	event.UserID = *userID
+
 	if prevEvent == nil || prevEvent.EventID() == event.EventID() {
 		return event, nil
 	}
diff --git a/syncapi/routing/search_test.go b/syncapi/routing/search_test.go
index f6d7fb4eb..c70abbd1b 100644
--- a/syncapi/routing/search_test.go
+++ b/syncapi/routing/search_test.go
@@ -230,7 +230,8 @@ func TestSearch(t *testing.T) {
 				stateEvents = append(stateEvents, x)
 				stateEventIDs = append(stateEventIDs, x.EventID())
 			}
-			sp, err = db.WriteEvent(processCtx.Context(), x, stateEvents, stateEventIDs, nil, nil, false, gomatrixserverlib.HistoryVisibilityShared)
+
+			sp, err = db.WriteEvent(processCtx.Context(), x, spec.UserID{}, stateEvents, stateEventIDs, nil, nil, false, gomatrixserverlib.HistoryVisibilityShared)
 			assert.NoError(t, err)
 			if x.Type() != "m.room.message" {
 				continue
diff --git a/syncapi/storage/postgres/current_room_state_table.go b/syncapi/storage/postgres/current_room_state_table.go
index bfe5e9bdd..112fa9d4a 100644
--- a/syncapi/storage/postgres/current_room_state_table.go
+++ b/syncapi/storage/postgres/current_room_state_table.go
@@ -343,9 +343,9 @@ func (s *currentRoomStateStatements) UpsertRoomState(
 		event.RoomID(),
 		event.EventID(),
 		event.Type(),
-		event.SenderID(),
+		event.UserID.String(),
 		containsURL,
-		*event.StateKey(),
+		*event.StateKeyResolved,
 		headeredJSON,
 		membership,
 		addedAt,
diff --git a/syncapi/storage/postgres/memberships_table.go b/syncapi/storage/postgres/memberships_table.go
index 3905f9abb..6bf9f61a1 100644
--- a/syncapi/storage/postgres/memberships_table.go
+++ b/syncapi/storage/postgres/memberships_table.go
@@ -109,7 +109,7 @@ func (s *membershipsStatements) UpsertMembership(
 	_, err = sqlutil.TxStmt(txn, s.upsertMembershipStmt).ExecContext(
 		ctx,
 		event.RoomID(),
-		*event.StateKey(),
+		event.UserID.String(),
 		membership,
 		event.EventID(),
 		streamPos,
diff --git a/syncapi/storage/postgres/output_room_events_table.go b/syncapi/storage/postgres/output_room_events_table.go
index e068afab1..b58cf59f0 100644
--- a/syncapi/storage/postgres/output_room_events_table.go
+++ b/syncapi/storage/postgres/output_room_events_table.go
@@ -407,7 +407,7 @@ func (s *outputRoomEventsStatements) InsertEvent(
 		event.EventID(),
 		headeredJSON,
 		event.Type(),
-		event.SenderID(),
+		event.UserID.String(),
 		containsURL,
 		pq.StringArray(addState),
 		pq.StringArray(removeState),
diff --git a/syncapi/storage/sqlite3/current_room_state_table.go b/syncapi/storage/sqlite3/current_room_state_table.go
index e432e483b..3bd19b367 100644
--- a/syncapi/storage/sqlite3/current_room_state_table.go
+++ b/syncapi/storage/sqlite3/current_room_state_table.go
@@ -342,9 +342,9 @@ func (s *currentRoomStateStatements) UpsertRoomState(
 		event.RoomID(),
 		event.EventID(),
 		event.Type(),
-		event.SenderID(),
+		event.UserID.String(),
 		containsURL,
-		*event.StateKey(),
+		*event.StateKeyResolved,
 		headeredJSON,
 		membership,
 		addedAt,
diff --git a/syncapi/storage/sqlite3/memberships_table.go b/syncapi/storage/sqlite3/memberships_table.go
index c09fa1510..6218ea660 100644
--- a/syncapi/storage/sqlite3/memberships_table.go
+++ b/syncapi/storage/sqlite3/memberships_table.go
@@ -112,7 +112,7 @@ func (s *membershipsStatements) UpsertMembership(
 	_, err = sqlutil.TxStmt(txn, s.upsertMembershipStmt).ExecContext(
 		ctx,
 		event.RoomID(),
-		*event.StateKey(),
+		event.UserID.String(),
 		membership,
 		event.EventID(),
 		streamPos,
diff --git a/syncapi/storage/sqlite3/output_room_events_table.go b/syncapi/storage/sqlite3/output_room_events_table.go
index 5a47aec44..06c65419a 100644
--- a/syncapi/storage/sqlite3/output_room_events_table.go
+++ b/syncapi/storage/sqlite3/output_room_events_table.go
@@ -348,7 +348,7 @@ func (s *outputRoomEventsStatements) InsertEvent(
 		event.EventID(),
 		headeredJSON,
 		event.Type(),
-		event.SenderID(),
+		event.UserID.String(),
 		containsURL,
 		string(addStateJSON),
 		string(removeStateJSON),
diff --git a/syncapi/sync/requestpool.go b/syncapi/sync/requestpool.go
index 5a92c70e1..cb5205d7f 100644
--- a/syncapi/sync/requestpool.go
+++ b/syncapi/sync/requestpool.go
@@ -503,6 +503,8 @@ func (rp *RequestPool) OnIncomingSyncRequest(req *http.Request, device *userapi.
 			}
 		}
 
+		logrus.Infof("%#v", syncReq.Response.Rooms.Join)
+
 		return util.JSONResponse{
 			Code: http.StatusOK,
 			JSON: syncReq.Response,