diff --git a/internal/backend.go b/internal/backend.go
index ac9f4f9..52b7b92 100644
--- a/internal/backend.go
+++ b/internal/backend.go
@@ -15,7 +15,6 @@ type Backend interface {
 	GetUserByToken(token string) (user User)
 	GetUserByName(userName string) User
 	GetRoomByID(id string) Room
-	Sync(token string, request sync.SyncRequest) (response *sync.SyncReply, err models.ApiError)
 	PublicRooms(filter string) []Room
 	ValidateUsernameFunc() func(string) error
 	GetEventByID(id string) events.Event
@@ -59,4 +58,5 @@ type User interface {
 	GetFilterByID(filterID string) *common.Filter
 	AddRoomAlias(Room, string) models.ApiError
 	DeleteRoomAlias(string) models.ApiError
+	Sync(token string, request sync.SyncRequest) (response *sync.SyncReply, err models.ApiError)
 }
diff --git a/internal/backends/memory/backend.go b/internal/backends/memory/backend.go
index e365a88..be03636 100644
--- a/internal/backends/memory/backend.go
+++ b/internal/backends/memory/backend.go
@@ -13,7 +13,6 @@ import (
 	"github.com/signaller-matrix/signaller/internal/models/common"
 	"github.com/signaller-matrix/signaller/internal/models/createroom"
 	"github.com/signaller-matrix/signaller/internal/models/events"
-	mSync "github.com/signaller-matrix/signaller/internal/models/sync"
 	"github.com/wangjia184/sortedset"
 )
 
@@ -89,13 +88,6 @@ func (backend *Backend) Login(username, password, device string) (user internal.
 	return user, token, nil
 }
 
-func (backend *Backend) Sync(token string, request mSync.SyncRequest) (response *mSync.SyncReply, err models.ApiError) {
-	backend.mutex.Lock()
-	defer backend.mutex.Unlock()
-
-	return nil, nil // TODO: implement
-}
-
 func (backend *Backend) GetUserByToken(token string) internal.User {
 	backend.mutex.RLock()
 	defer backend.mutex.RUnlock()
diff --git a/internal/backends/memory/user.go b/internal/backends/memory/user.go
index 7c63660..ced850a 100644
--- a/internal/backends/memory/user.go
+++ b/internal/backends/memory/user.go
@@ -11,6 +11,7 @@ import (
 	"github.com/signaller-matrix/signaller/internal/models/createroom"
 	"github.com/signaller-matrix/signaller/internal/models/devices"
 	"github.com/signaller-matrix/signaller/internal/models/events"
+	mSync "github.com/signaller-matrix/signaller/internal/models/sync"
 )
 
 type User struct {
@@ -351,3 +352,7 @@ func (user *User) GetFilterByID(filterID string) *common.Filter {
 
 	return nil
 }
+
+func (user *User) Sync(token string, request mSync.SyncRequest) (response *mSync.SyncReply, err models.ApiError) {
+	return nil, nil
+}
diff --git a/internal/handlers.go b/internal/handlers.go
index 4b1c417..e282b58 100644
--- a/internal/handlers.go
+++ b/internal/handlers.go
@@ -281,18 +281,24 @@ func SyncHandler(w http.ResponseWriter, r *http.Request) {
 
 	timeout, err := strconv.Atoi(r.FormValue("timeout"))
 	if err != nil {
-		errorResponse(w, models.M_UNKNOWN, http.StatusBadRequest, "timeout parse failes")
+		errorResponse(w, models.M_UNKNOWN, http.StatusBadRequest, "timeout parse failed")
 		return
 	}
 	request.Timeout = timeout
 
 	token := getTokenFromResponse(r)
 	if token == "" {
-		errorResponse(w, models.M_MISSING_TOKEN, http.StatusBadRequest, "")
+		errorResponse(w, models.M_FORBIDDEN, http.StatusForbidden, "")
 		return
 	}
 
-	response, _ := currServer.Backend.Sync(token, request) // TODO: handle error
+	user := currServer.Backend.GetUserByToken(token)
+	if user == nil {
+		errorResponse(w, models.M_UNKNOWN_TOKEN, http.StatusBadRequest, "")
+		return
+	}
+
+	response, _ := user.Sync(token, request) // TODO: handle error
 
 	response.NextBatch = "123"
 	response.Rooms = mSync.RoomsSyncReply{}