diff --git a/service_provider.go b/service_provider.go
index 30b35670..fa75f706 100644
--- a/service_provider.go
+++ b/service_provider.go
@@ -1672,7 +1672,11 @@ func elementToBytes(el *etree.Element) ([]byte, error) {
 	doc := etree.NewDocument()
 	doc.SetRoot(el.Copy())
 	for space, uri := range namespaces {
-		doc.Root().CreateAttr("xmlns:"+space, uri)
+		if space == "" {
+			doc.Root().CreateAttr("xmlns", uri)
+		} else {
+			doc.Root().CreateAttr("xmlns:"+space, uri)
+		}
 	}
 
 	return doc.WriteToBytes()