diff --git a/dataswamp/namespace/valueobjects.go b/dataswamp/namespace/valueobjects.go
index 4dd6ea6..421ffea 100644
--- a/dataswamp/namespace/valueobjects.go
+++ b/dataswamp/namespace/valueobjects.go
@@ -5,32 +5,36 @@ type FileSizeQuota struct {
 	CurrentUsage int64
 }
 
-func (f *FileSizeQuota) Allows(size int64) bool {
+func (f FileSizeQuota) Allows(size int64) bool {
 	return f.Remaining() >= size
 }
 
-func (f *FileSizeQuota) Remaining() int64 {
+func (f FileSizeQuota) Remaining() int64 {
 	return f.AllowanceKB - f.CurrentUsage
 }
 
-func (f *FileSizeQuota) Add(size int64) error {
+func (f FileSizeQuota) Add(size int64) (*FileSizeQuota, error) {
 	if !f.Allows(size) {
-		return ErrExceedQuota
+		return nil, ErrExceedQuota
 	}
 
-	f.CurrentUsage += size
-
-	return nil
+	n := FileSizeQuota {
+		f.AllowanceKB,
+		f.CurrentUsage + size,
+	}
+	return &n, nil
 }
 
-func (f *FileSizeQuota) Remove(size int64) error {
+func (f FileSizeQuota) Remove(size int64) (*FileSizeQuota, error) {
 	if size > f.CurrentUsage {
-		return ErrQuotaInvalid
+		return nil, ErrQuotaInvalid
 	}
 
-	f.CurrentUsage -= size
-
-	return nil
+	n := FileSizeQuota {
+		f.AllowanceKB,
+		f.CurrentUsage - size,
+	}
+	return &n, nil
 }
 
 type FileStat struct {
diff --git a/dataswamp/namespace/valueobjects_test.go b/dataswamp/namespace/valueobjects_test.go
index 7133e6e..4e1b6ba 100644
--- a/dataswamp/namespace/valueobjects_test.go
+++ b/dataswamp/namespace/valueobjects_test.go
@@ -15,23 +15,27 @@ func TestQuota(t *testing.T) {
 
 func TestQuotaManipulation(t *testing.T) {
 	is := is.New(t)
-	quota := FileSizeQuota{1000, 0}
-
-	is.NoErr(quota.Add(500))
+	quota := &FileSizeQuota{1000, 0}
+	quota, err := quota.Add(500)
+	is.NoErr(err)
 
 	is.Equal(quota.CurrentUsage, int64(500))
 
-	is.NoErr(quota.Add(500))
+	quota, err = quota.Add(500)
+	is.NoErr(err)
 
-	is.Equal(quota.Add(1), ErrExceedQuota)
+	_ , err = quota.Add(1)
+	is.Equal(err, ErrExceedQuota)
 
 	is.Equal(quota.CurrentUsage, int64(1000))
 
-	is.Equal(quota.Remove(1001), ErrQuotaInvalid)
+	_ , err = quota.Remove(1001)
+	is.Equal(err, ErrQuotaInvalid)
 
 	is.Equal(quota.CurrentUsage, int64(1000))
 
-	is.NoErr(quota.Remove(1000))
+	quota, err = quota.Remove(1000)
+	is.NoErr(err)
 
 	is.Equal(quota.CurrentUsage, int64(0))
 }
diff --git a/dataswamp/services.go b/dataswamp/services.go
index caefe28..a36cad1 100644
--- a/dataswamp/services.go
+++ b/dataswamp/services.go
@@ -61,7 +61,7 @@ func (s SwampFileService) getOrCreateNs(namespace_in string) *namespace.Namespac
 func (s SwampFileService) SaveFile(ref swampfile.FileReference, src io.Reader, size int64) error {
 	ns := s.getOrCreateNs(ref.UserAgent)
 
-	err := ref.Clean(true)
+	r, err := ref.Clean(true)
 
 	if err != nil {
 		return err
@@ -71,7 +71,7 @@ func (s SwampFileService) SaveFile(ref swampfile.FileReference, src io.Reader, s
 		return namespace.ErrExceedQuota
 	}
 
-	f, err := s.swamp_file_repo.Create(ref.Path, strconv.FormatInt(ns.ID, 10))
+	f, err := s.swamp_file_repo.Create(r.Path, strconv.FormatInt(ns.ID, 10))
 
 	if err != nil {
 		return err
@@ -80,7 +80,7 @@ func (s SwampFileService) SaveFile(ref swampfile.FileReference, src io.Reader, s
 	written, err := io.CopyN(f, src, size)
 
 	if written < size {
-		s.swamp_file_repo.Delete(ref.Path, strconv.FormatInt(ns.ID, 10))
+		s.swamp_file_repo.Delete(r.Path, strconv.FormatInt(ns.ID, 10))
 		return swampfile.ErrContentSizeExaggerated
 	}
 
@@ -89,12 +89,16 @@ func (s SwampFileService) SaveFile(ref swampfile.FileReference, src io.Reader, s
 	overread, err := src.Read(buf)
 
 	if overread > 0 || err != io.EOF {
-		s.swamp_file_repo.Delete(ref.Path, strconv.FormatInt(ns.ID, 10))
+		s.swamp_file_repo.Delete(r.Path, strconv.FormatInt(ns.ID, 10))
 		return swampfile.ErrContentSizeExceeded
 	}
 
 	f.Close()
-	ns.FileQuota.Add(size)
+	uq, err := ns.FileQuota.Add(size)
+	if err != nil {
+		return err
+	}
+	ns.FileQuota = *uq
 	ns.Usage = ns.Usage.Add(size)
 	ns.Upload = ns.Upload.Add(size)
 	s.namespace_repo.Update(ns.ID, *ns)
@@ -105,13 +109,13 @@ func (s SwampFileService) SaveFile(ref swampfile.FileReference, src io.Reader, s
 func (s SwampFileService) OpenOutFile(ref swampfile.FileReference) (swampfile.SwampOutFile, error) {
 	ns := s.getOrCreateNs(ref.UserAgent)
 
-	err := ref.Clean(true)
+	r, err := ref.Clean(true)
 
 	if err != nil {
 		return nil, err
 	}
 
-	f, err := s.swamp_file_repo.Open(ref.Path, strconv.FormatInt(ns.ID, 10))
+	f, err := s.swamp_file_repo.Open(r.Path, strconv.FormatInt(ns.ID, 10))
 
 	if err != nil {
 		return nil, err
@@ -140,7 +144,11 @@ func (s SwampFileService) CleanUpExpiredFiles() error {
 		dfs, err := s.swamp_file_repo.DeleteOlderThan(strconv.FormatInt(ns.ID, 10), expiry)
 
 		for _, df := range dfs {
-			ns.FileQuota.Remove(df.Size)
+			dq, err := ns.FileQuota.Remove(df.Size)
+			if err != nil {
+				dq.CurrentUsage = 0
+			}
+			ns.FileQuota = *dq
 		}
 
 		if err != nil {
diff --git a/dataswamp/swampfile/valueobjects.go b/dataswamp/swampfile/valueobjects.go
index 9bec9c2..c3f00f5 100644
--- a/dataswamp/swampfile/valueobjects.go
+++ b/dataswamp/swampfile/valueobjects.go
@@ -36,14 +36,17 @@ type DeletedSwampFile struct {
 	Size int64
 }
 
-func (fr *FileReference) Clean(strict bool) error {
+func (fr *FileReference) Clean(strict bool) (*FileReference, error) {
 	c := filepath.FromSlash(path.Clean("/" + strings.Trim(fr.Path, "/")))
 
 	if c != fr.Path && strict {
-		return ErrUnacceptablePath
+		return nil, ErrUnacceptablePath
 	}
 
-	fr.Path = c
+	n := FileReference {
+		c,
+		fr.UserAgent,
+	}
 
-	return nil
+	return &n, nil
 }
diff --git a/dataswamp/swampfile/valueobjects_test.go b/dataswamp/swampfile/valueobjects_test.go
index a4a5c3b..c2fa840 100644
--- a/dataswamp/swampfile/valueobjects_test.go
+++ b/dataswamp/swampfile/valueobjects_test.go
@@ -25,9 +25,9 @@ func TestSwampPathNotStrict(t *testing.T) {
 			"ns",
 		}
 
-		err := rf.Clean(false)
+		rc, err := rf.Clean(false)
 		is.NoErr(err)
-		is.Equal(rf.Path, tc.clean)
+		is.Equal(rc.Path, tc.clean)
 	}
 }
 
@@ -39,6 +39,6 @@ func TestSwampPathStrict(t *testing.T) {
 		"ns",
 	}
 
-	err := rf.Clean(true)
+	_, err := rf.Clean(true)
 	is.Equal(err, ErrUnacceptablePath)
 }