diff --git a/pkg/publicshare/manager/json/json.go b/pkg/publicshare/manager/json/json.go
index 9e4c1a17021..4d61b297517 100644
--- a/pkg/publicshare/manager/json/json.go
+++ b/pkg/publicshare/manager/json/json.go
@@ -363,16 +363,19 @@ func (m *manager) ListPublicShares(ctx context.Context, u *user.User, filters []
 // RevokePublicShare undocumented.
 func (m *manager) RevokePublicShare(ctx context.Context, u *user.User, ref *link.PublicShareReference) error {
 	m.mutex.Lock()
-	defer m.mutex.Unlock()
-
 	db, err := m.readDb()
 	if err != nil {
 		return err
 	}
+	m.mutex.Unlock()
 
 	switch {
-	case ref.GetId().OpaqueId != "":
-		delete(db, ref.GetId().OpaqueId)
+	case ref.GetId() != nil && ref.GetId().OpaqueId != "":
+		if _, ok := db[ref.GetId().OpaqueId]; ok {
+			delete(db, ref.GetId().OpaqueId)
+		} else {
+			return errors.New("reference does not exist")
+		}
 	case ref.GetToken() != "":
 		share, err := m.getByToken(ctx, ref.GetToken())
 		if err != nil {
@@ -383,6 +386,8 @@ func (m *manager) RevokePublicShare(ctx context.Context, u *user.User, ref *link
 		return errors.New("reference does not exist")
 	}
 
+	m.mutex.Lock()
+	defer m.mutex.Unlock()
 	return m.writeDb(db)
 }
 
diff --git a/pkg/publicshare/manager/memory/memory.go b/pkg/publicshare/manager/memory/memory.go
index e8c3372785e..6f3e8f14219 100644
--- a/pkg/publicshare/manager/memory/memory.go
+++ b/pkg/publicshare/manager/memory/memory.go
@@ -194,7 +194,7 @@ func (m *manager) ListPublicShares(ctx context.Context, u *user.User, filters []
 func (m *manager) RevokePublicShare(ctx context.Context, u *user.User, ref *link.PublicShareReference) error {
 	// check whether the reference exists
 	switch {
-	case ref.GetId().OpaqueId != "":
+	case ref.GetId() != nil && ref.GetId().OpaqueId != "":
 		s, err := m.getPublicShareByTokenID(ctx, *ref.GetId())
 		if err != nil {
 			return errors.New("reference does not exist")