diff --git a/src/github.com/matrix-org/dendrite/cmd/dendrite-room-server/main.go b/src/github.com/matrix-org/dendrite/cmd/dendrite-room-server/main.go
index f607d1ec2..06773972a 100644
--- a/src/github.com/matrix-org/dendrite/cmd/dendrite-room-server/main.go
+++ b/src/github.com/matrix-org/dendrite/cmd/dendrite-room-server/main.go
@@ -20,7 +20,6 @@ import (
 	_ "net/http/pprof"
 	"os"
 
-	log "github.com/sirupsen/logrus"
 	"github.com/matrix-org/dendrite/common"
 	"github.com/matrix-org/dendrite/common/config"
 	"github.com/matrix-org/dendrite/roomserver/alias"
@@ -28,6 +27,7 @@ import (
 	"github.com/matrix-org/dendrite/roomserver/query"
 	"github.com/matrix-org/dendrite/roomserver/storage"
 	"github.com/prometheus/client_golang/prometheus"
+	log "github.com/sirupsen/logrus"
 	sarama "gopkg.in/Shopify/sarama.v1"
 )
 
diff --git a/src/github.com/matrix-org/dendrite/roomserver/query/query.go b/src/github.com/matrix-org/dendrite/roomserver/query/query.go
index c897a9b4e..bddc9cf86 100644
--- a/src/github.com/matrix-org/dendrite/roomserver/query/query.go
+++ b/src/github.com/matrix-org/dendrite/roomserver/query/query.go
@@ -16,8 +16,10 @@ package query
 
 import (
 	"context"
+	"database/sql"
 	"encoding/json"
 	"net/http"
+	"time"
 
 	"github.com/matrix-org/dendrite/common"
 	"github.com/matrix-org/dendrite/roomserver/api"
@@ -74,6 +76,10 @@ type RoomserverQueryAPIDatabase interface {
 	EventStateKeys(
 		context.Context, []types.EventStateKeyNID,
 	) (map[types.EventStateKeyNID]string, error)
+	// Lookup if the roomID has been reserved, and when that reservation was made.
+	RoomIDReserved(ctx context.Context, roomID string) (time.Time, error)
+	// Reserve the room ID.
+	ReserveRoomID(ctx context.Context, roomID string) error
 }
 
 // RoomserverQueryAPI is an implementation of api.RoomserverQueryAPI
@@ -425,14 +431,34 @@ func (r *RoomserverQueryAPI) QueryReserveRoomID(
 	response *api.QueryReserveRoomIDResponse,
 ) error {
 	nid, err := r.DB.RoomNID(ctx, request.RoomID)
+	if err != nil && err != sql.ErrNoRows {
+		return err
+	}
+
 	if nid != 0 {
 		response.Success = false
 		return nil
 	}
 
+	// Check if Room ID has already been reserved.
+	reservedSince, err := r.DB.RoomIDReserved(ctx, request.RoomID)
+	if reservedSince != (time.Time{}) {
+		response.Success = false
+		return nil
+	}
+
+	if err != nil && err != sql.ErrNoRows {
+		return err
+	}
+
+	err = r.DB.ReserveRoomID(ctx, request.RoomID)
+	if err != nil {
+		return err
+	}
+
 	response.Success = true
 
-	return err
+	return nil
 }
 
 // SetupHTTP adds the RoomserverQueryAPI handlers to the http.ServeMux.
diff --git a/src/github.com/matrix-org/dendrite/roomserver/storage/sql.go b/src/github.com/matrix-org/dendrite/roomserver/storage/sql.go
index a24dbb1d3..1a8f497f5 100644
--- a/src/github.com/matrix-org/dendrite/roomserver/storage/sql.go
+++ b/src/github.com/matrix-org/dendrite/roomserver/storage/sql.go
@@ -30,6 +30,7 @@ type statements struct {
 	roomAliasesStatements
 	inviteStatements
 	membershipStatements
+	reservedRoomStatements
 }
 
 func (s *statements) prepare(db *sql.DB) error {
@@ -47,6 +48,7 @@ func (s *statements) prepare(db *sql.DB) error {
 		s.roomAliasesStatements.prepare,
 		s.inviteStatements.prepare,
 		s.membershipStatements.prepare,
+		s.reservedRoomStatements.prepare,
 	} {
 		if err = prepare(db); err != nil {
 			return err
diff --git a/src/github.com/matrix-org/dendrite/roomserver/storage/storage.go b/src/github.com/matrix-org/dendrite/roomserver/storage/storage.go
index ad4fed659..ee812710a 100644
--- a/src/github.com/matrix-org/dendrite/roomserver/storage/storage.go
+++ b/src/github.com/matrix-org/dendrite/roomserver/storage/storage.go
@@ -17,6 +17,7 @@ package storage
 import (
 	"context"
 	"database/sql"
+	"time"
 
 	// Import the postgres database driver.
 	_ "github.com/lib/pq"
@@ -651,6 +652,17 @@ func (d *Database) GetMembershipEventNIDsForRoom(
 	return d.statements.selectMembershipsFromRoom(ctx, roomNID)
 }
 
+// RoomIDReserved implements query.RoomserverQueryAPIDB
+func (d *Database) RoomIDReserved(ctx context.Context, roomID string) (time.Time, error) {
+	return d.statements.selectReservedRoom(ctx, roomID)
+}
+
+// ReserveRoomID implements query.RoomserverQueryAPIDB
+// It saved the given room ID as reserved.
+func (d *Database) ReserveRoomID(ctx context.Context, roomID string) error {
+	return d.statements.insertReservedRoom(ctx, roomID, time.Now())
+}
+
 type transaction struct {
 	ctx context.Context
 	txn *sql.Tx