diff --git a/internal/objectstorage/objectstorage.go b/internal/objectstorage/objectstorage.go
index ddf5a4d..86c4126 100644
--- a/internal/objectstorage/objectstorage.go
+++ b/internal/objectstorage/objectstorage.go
@@ -23,6 +23,11 @@ import (
 type Storage interface {
 	Stat(filepath string) (*types.ObjectInfo, error)
 	ReadObject(filepath string) (types.ReadSeekCloser, error)
+	// WriteObject atomically writes an object. If size is greater or equal to
+	// zero then only size bytes will be read from data and wrote. If size is
+	// less than zero data will be wrote until EOF. When persist is true the
+	// implementation must ensure that data is persisted to the underlying
+	// storage.
 	WriteObject(filepath string, data io.Reader, size int64, persist bool) error
 	DeleteObject(filepath string) error
 	List(prefix, startWith, delimiter string, doneCh <-chan struct{}) <-chan types.ObjectInfo
diff --git a/internal/objectstorage/posix/posix.go b/internal/objectstorage/posix/posix.go
index c44a184..8a4201d 100644
--- a/internal/objectstorage/posix/posix.go
+++ b/internal/objectstorage/posix/posix.go
@@ -98,9 +98,13 @@ func (s *PosixStorage) WriteObject(p string, data io.Reader, size int64, persist
 	if err := os.MkdirAll(path.Dir(fspath), 0770); err != nil {
 		return err
 	}
-	lr := io.LimitReader(data, size)
+
+	r := data
+	if size >= 0 {
+		r = io.LimitReader(data, size)
+	}
 	return common.WriteFileAtomicFunc(fspath, s.dataDir, s.tmpDir, 0660, persist, func(f io.Writer) error {
-		_, err := io.Copy(f, lr)
+		_, err := io.Copy(f, r)
 		return err
 	})
 }
diff --git a/internal/objectstorage/posixflat/posixflat.go b/internal/objectstorage/posixflat/posixflat.go
index e70afe6..d3e4a7c 100644
--- a/internal/objectstorage/posixflat/posixflat.go
+++ b/internal/objectstorage/posixflat/posixflat.go
@@ -274,9 +274,13 @@ func (s *PosixFlatStorage) WriteObject(p string, data io.Reader, size int64, per
 	if err := os.MkdirAll(path.Dir(fspath), 0770); err != nil {
 		return err
 	}
-	lr := io.LimitReader(data, size)
+
+	r := data
+	if size >= 0 {
+		r = io.LimitReader(data, size)
+	}
 	return common.WriteFileAtomicFunc(fspath, s.dataDir, s.tmpDir, 0660, persist, func(f io.Writer) error {
-		_, err := io.Copy(f, lr)
+		_, err := io.Copy(f, r)
 		return err
 	})
 }