diff --git a/pkg/storage/donut/donutdriver_test.go b/pkg/storage/donut/donutdriver_test.go
index ed6e10c27..d4bd93e99 100644
--- a/pkg/storage/donut/donutdriver_test.go
+++ b/pkg/storage/donut/donutdriver_test.go
@@ -204,3 +204,21 @@ func (s *MySuite) TestMultipleNewObjects(c *C) {
 	c.Assert(err, IsNil)
 	c.Assert(listObjects, DeepEquals, []string{"obj1", "obj2"})
 }
+
+func (s *MySuite) TestSysPrefixShouldFail(c *C) {
+	root, err := ioutil.TempDir(os.TempDir(), "donut-")
+	c.Assert(err, IsNil)
+	defer os.RemoveAll(root)
+	donut := NewDonutDriver(root)
+
+	c.Assert(donut.CreateBucket("foo"), IsNil)
+	writer, err := donut.GetObjectWriter("foo", "obj1")
+	c.Assert(err, IsNil)
+	writer.Write([]byte("one"))
+	metadata := make(map[string]string)
+	metadata["foo"] = "bar"
+	metadata["sys.hello"] = "world"
+	err = writer.SetMetadata(metadata)
+	c.Assert(err, Not(IsNil))
+	writer.Close()
+}
diff --git a/pkg/storage/donut/erasure.go b/pkg/storage/donut/erasure.go
index 36b2eb0fa..4c85eafc5 100644
--- a/pkg/storage/donut/erasure.go
+++ b/pkg/storage/donut/erasure.go
@@ -11,6 +11,7 @@ import (
 	"errors"
 	"github.com/minio-io/minio/pkg/encoding/erasure"
 	"github.com/minio-io/minio/pkg/utils/split"
+	"strings"
 )
 
 func erasureReader(readers []io.ReadCloser, donutMetadata map[string]string, writer *io.PipeWriter) {
@@ -108,8 +109,8 @@ func erasureGoroutine(r *io.PipeReader, eWriter erasureWriter, isClosed chan<- b
 	metadata["erasureK"] = "8"
 	metadata["erasureM"] = "8"
 	metadata["erasureTechnique"] = "Cauchy"
-	metadata["totalLength"] = strconv.Itoa(totalLength)
 	metadata["md5"] = hex.EncodeToString(dataMd5sum)
+	metadata["totalLength"] = strconv.Itoa(totalLength)
 	for _, nodeWriter := range eWriter.writers {
 		if nodeWriter != nil {
 			nodeWriter.SetMetadata(eWriter.metadata)
@@ -141,6 +142,11 @@ func (d erasureWriter) CloseWithError(err error) error {
 }
 
 func (d erasureWriter) SetMetadata(metadata map[string]string) error {
+	for k, _ := range metadata {
+		if strings.HasPrefix(k, "sys.") {
+			return errors.New("Invalid key '" + k + "', cannot start with sys.'")
+		}
+	}
 	for k := range d.metadata {
 		delete(d.metadata, k)
 	}