diff --git a/pkg/storage/favorite/favorite.go b/pkg/storage/favorite/favorite.go
index 7e441d36870..312c346dbce 100644
--- a/pkg/storage/favorite/favorite.go
+++ b/pkg/storage/favorite/favorite.go
@@ -20,6 +20,7 @@ package favorite
 
 import (
 	"context"
+	"sync"
 
 	user "github.com/cs3org/go-cs3apis/cs3/identity/user/v1beta1"
 	provider "github.com/cs3org/go-cs3apis/cs3/storage/provider/v1beta1"
@@ -37,17 +38,20 @@ type Manager interface {
 
 // NewInMemoryManager returns an instance of the in-memory favorites manager.
 func NewInMemoryManager() Manager {
-	return InMemoryManager{favorites: make(map[string]map[string]*provider.ResourceId)}
+	return &InMemoryManager{favorites: make(map[string]map[string]*provider.ResourceId)}
 }
 
 // InMemoryManager implements the Manager interface to manage favorites using an in-memory storage.
 // This should not be used in production but can be used for tests.
 type InMemoryManager struct {
+	mux       sync.RWMutex
 	favorites map[string]map[string]*provider.ResourceId
 }
 
 // ListFavorites returns all resources that were favorited by a user.
-func (m InMemoryManager) ListFavorites(ctx context.Context, userID *user.UserId) ([]*provider.ResourceId, error) {
+func (m *InMemoryManager) ListFavorites(ctx context.Context, userID *user.UserId) ([]*provider.ResourceId, error) {
+	m.mux.RLock()
+	defer m.mux.RUnlock()
 	favorites := make([]*provider.ResourceId, 0, len(m.favorites[userID.OpaqueId]))
 	for _, id := range m.favorites[userID.OpaqueId] {
 		favorites = append(favorites, id)
@@ -56,7 +60,9 @@ func (m InMemoryManager) ListFavorites(ctx context.Context, userID *user.UserId)
 }
 
 // SetFavorite marks a resource as favorited by a user.
-func (m InMemoryManager) SetFavorite(_ context.Context, userID *user.UserId, resourceID *provider.ResourceId) error {
+func (m *InMemoryManager) SetFavorite(_ context.Context, userID *user.UserId, resourceID *provider.ResourceId) error {
+	m.mux.Lock()
+	defer m.mux.Unlock()
 	if m.favorites[userID.OpaqueId] == nil {
 		m.favorites[userID.OpaqueId] = make(map[string]*provider.ResourceId)
 	}
@@ -65,7 +71,9 @@ func (m InMemoryManager) SetFavorite(_ context.Context, userID *user.UserId, res
 }
 
 // UnsetFavorite unmarks a resource as favorited by a user.
-func (m InMemoryManager) UnsetFavorite(_ context.Context, userID *user.UserId, resourceID *provider.ResourceId) error {
+func (m *InMemoryManager) UnsetFavorite(_ context.Context, userID *user.UserId, resourceID *provider.ResourceId) error {
+	m.mux.Lock()
+	defer m.mux.Unlock()
 	delete(m.favorites[userID.OpaqueId], resourceID.OpaqueId)
 	return nil
 }