diff --git a/internal/grpc/services/gateway/storageprovider.go b/internal/grpc/services/gateway/storageprovider.go
index e7bafde9856..c944a293510 100644
--- a/internal/grpc/services/gateway/storageprovider.go
+++ b/internal/grpc/services/gateway/storageprovider.go
@@ -169,7 +169,7 @@ func (s *svc) ListStorageSpaces(ctx context.Context, req *provider.ListStorageSp
 			}, nil
 		}
 
-		providers = []*registry.ProviderInfo{}
+		providers = make([]*registry.ProviderInfo, 0, len(res.Providers))
 		// FIXME filter only providers that have an id set ... currently none have?
 		// bug? only ProviderPath is set
 		for i := range res.Providers {
@@ -201,7 +201,7 @@ func (s *svc) ListStorageSpaces(ctx context.Context, req *provider.ListStorageSp
 			uniqueSpaces[spacesFromProviders[i][j].Id.OpaqueId] = spacesFromProviders[i][j]
 		}
 	}
-	spaces := []*provider.StorageSpace{}
+	spaces := make([]*provider.StorageSpace, 0, len(uniqueSpaces))
 	for spaceID := range uniqueSpaces {
 		spaces = append(spaces, uniqueSpaces[spaceID])
 	}
diff --git a/pkg/storage/fs/owncloudsql/owncloudsql.go b/pkg/storage/fs/owncloudsql/owncloudsql.go
index a9d5e784fec..186d279ef68 100644
--- a/pkg/storage/fs/owncloudsql/owncloudsql.go
+++ b/pkg/storage/fs/owncloudsql/owncloudsql.go
@@ -2162,7 +2162,7 @@ func (fs *ocfs) HashFile(path string) (string, string, string, error) {
 
 func (fs *ocfs) ListStorageSpaces(ctx context.Context, filter []*provider.ListStorageSpacesRequest_Filter) ([]*provider.StorageSpace, error) {
 	// TODO(corby): Implement
-	return nil, nil
+	return nil, errtypes.NotSupported("list storage spaces")
 }
 
 func readChecksumIntoResourceChecksum(ctx context.Context, checksums, algo string, ri *provider.ResourceInfo) {
diff --git a/pkg/storage/utils/decomposedfs/decomposedfs.go b/pkg/storage/utils/decomposedfs/decomposedfs.go
index e524bf2d409..d2f649d454c 100644
--- a/pkg/storage/utils/decomposedfs/decomposedfs.go
+++ b/pkg/storage/utils/decomposedfs/decomposedfs.go
@@ -530,7 +530,7 @@ func (fs *Decomposedfs) ListStorageSpaces(ctx context.Context, filter []*provide
 		return nil, err
 	}
 
-	var spaces []*provider.StorageSpace
+	spaces := make([]*provider.StorageSpace, 0, len(matches))
 
 	u, ok := user.ContextGetUser(ctx)
 	if !ok {
@@ -628,12 +628,10 @@ func (fs *Decomposedfs) ListStorageSpaces(ctx context.Context, filter []*provide
 				// -1 = uncalculated
 				// -2 = unknown
 				// -3 = unlimited
-				if quota, err := strconv.ParseInt(string(v), 10, 64); err == nil {
-					if quota >= 0 {
-						space.Quota = &provider.Quota{
-							QuotaMaxBytes: uint64(quota),
-							QuotaMaxFiles: math.MaxUint64, // TODO MaxUInt64? = unlimited? why even max files? 0 = unlimited?
-						}
+				if quota, err := strconv.ParseUint(string(v), 10, 64); err == nil {
+					space.Quota = &provider.Quota{
+						QuotaMaxBytes: quota,
+						QuotaMaxFiles: math.MaxUint64, // TODO MaxUInt64? = unlimited? why even max files? 0 = unlimited?
 					}
 				} else {
 					appctx.GetLogger(ctx).Debug().Err(err).Str("nodepath", matches[i]).Msg("could not read quota")