diff --git a/instant-xml-macros/src/lib.rs b/instant-xml-macros/src/lib.rs
index b2ec26e..b5380a1 100644
--- a/instant-xml-macros/src/lib.rs
+++ b/instant-xml-macros/src/lib.rs
@@ -39,9 +39,9 @@ pub fn to_xml(input: TokenStream) -> TokenStream {
 
     let ident = &ast.ident;
     let root_name = ident.to_string();
-    let mut header: String = root_name.to_string();
-    if let Some(v) = retrieve_default_namespace(&ast) {
-        header += format!(" xmlns=\"{}\"", v).as_str();
+    let header = match retrieve_default_namespace(&ast) {
+        Some(ns) => format!("{} xmlns=\"{}\"", root_name, ns),
+        None => root_name.clone(),
     };
 
     let mut output: proc_macro2::TokenStream =