diff --git a/roomserver/storage/interface.go b/roomserver/storage/interface.go
index 149d5849b..c048ac3d6 100644
--- a/roomserver/storage/interface.go
+++ b/roomserver/storage/interface.go
@@ -204,7 +204,8 @@ type UserRoomKeys interface {
 	InsertUserRoomPublicKey(ctx context.Context, userID spec.UserID, roomID spec.RoomID, key ed25519.PublicKey) (result ed25519.PublicKey, err error)
 	// SelectUserRoomPrivateKey selects the private key for the given user and room combination
 	SelectUserRoomPrivateKey(ctx context.Context, userID spec.UserID, roomID spec.RoomID) (key ed25519.PrivateKey, err error)
-	// SelectUserIDsForPublicKeys selects all userIDs for the requested senderKeys. Returns a map from roomID -> map from publicKey to userID
+	// SelectUserIDsForPublicKeys selects all userIDs for the requested senderKeys. Returns a map from roomID -> map from publicKey to userID.
+	// If a senderKey can't be found, it is omitted in the result.
 	SelectUserIDsForPublicKeys(ctx context.Context, publicKeys map[spec.RoomID][]ed25519.PublicKey) (map[spec.RoomID]map[string]string, error)
 }
 
diff --git a/roomserver/storage/postgres/user_room_keys_table.go b/roomserver/storage/postgres/user_room_keys_table.go
index 630f5afba..22f978bf0 100644
--- a/roomserver/storage/postgres/user_room_keys_table.go
+++ b/roomserver/storage/postgres/user_room_keys_table.go
@@ -51,7 +51,7 @@ const insertUserRoomPublicKeySQL = `
 
 const selectUserRoomKeySQL = `SELECT pseudo_id_key FROM roomserver_user_room_keys WHERE user_nid = $1 AND room_nid = $2`
 
-const selectUserNIDsSQL = `SELECT user_nid, room_nid, pseudo_id_pub_key FROM roomserver_user_room_keys WHERE pseudo_id_pub_key = ANY($1)`
+const selectUserNIDsSQL = `SELECT user_nid, room_nid, pseudo_id_pub_key FROM roomserver_user_room_keys WHERE room_nid = ANY($1) AND pseudo_id_pub_key = ANY($2)`
 
 type userRoomKeysStatements struct {
 	insertUserRoomPrivateKeyStmt *sql.Stmt
@@ -113,7 +113,7 @@ func (s *userRoomKeysStatements) BulkSelectUserNIDs(ctx context.Context, txn *sq
 			senders = append(senders, key)
 		}
 	}
-	rows, err := stmt.QueryContext(ctx, pq.Array(senders))
+	rows, err := stmt.QueryContext(ctx, pq.Array(roomNIDs), pq.Array(senders))
 	if err != nil {
 		return nil, err
 	}
diff --git a/roomserver/storage/shared/storage.go b/roomserver/storage/shared/storage.go
index 4466b5b28..a01d393d9 100644
--- a/roomserver/storage/shared/storage.go
+++ b/roomserver/storage/shared/storage.go
@@ -1733,14 +1733,14 @@ func (d *Database) SelectUserIDsForPublicKeys(ctx context.Context, publicKeys ma
 			nids = append(nids, nid.EventStateKeyNID)
 		}
 		// get the userIDs
-		nidMAP, seErr := d.EventStateKeys(ctx, nids)
+		nidMap, seErr := d.EventStateKeys(ctx, nids)
 		if seErr != nil {
 			return seErr
 		}
 
 		// build the result map (roomID -> map publicKey -> userID)
 		for publicKey, userRoomKeyPair := range userRoomKeyPairMap {
-			userID := nidMAP[userRoomKeyPair.EventStateKeyNID]
+			userID := nidMap[userRoomKeyPair.EventStateKeyNID]
 			roomID := rooms[userRoomKeyPair.RoomNID]
 			resMap, exists := result[roomID]
 			if !exists {
diff --git a/roomserver/storage/tables/interface.go b/roomserver/storage/tables/interface.go
index 8f2422a32..cd0e51686 100644
--- a/roomserver/storage/tables/interface.go
+++ b/roomserver/storage/tables/interface.go
@@ -194,6 +194,7 @@ type UserRoomKeys interface {
 	// SelectUserRoomPrivateKey selects the private key for the given user and room combination
 	SelectUserRoomPrivateKey(ctx context.Context, txn *sql.Tx, userNID types.EventStateKeyNID, roomNID types.RoomNID) (ed25519.PrivateKey, error)
 	// BulkSelectUserNIDs selects all userIDs for the requested senderKeys. Returns a map from publicKey -> types.UserRoomKeyPair.
+	// If a senderKey can't be found, it is omitted in the result.
 	BulkSelectUserNIDs(ctx context.Context, txn *sql.Tx, senderKeys map[types.RoomNID][]ed25519.PublicKey) (map[string]types.UserRoomKeyPair, error)
 }