diff --git a/yaserde/src/lib.rs b/yaserde/src/lib.rs
index 3a6a444..290829b 100644
--- a/yaserde/src/lib.rs
+++ b/yaserde/src/lib.rs
@@ -325,7 +325,7 @@ macro_rules! serialize_and_validate {
     log::debug!("serialize_and_validate @ {}:{}", file!(), line!());
     let data: Result<String, String> = yaserde::ser::to_string(&$model);
 
-    let content = format!(r#"<?xml version="1.0" encoding="utf-8"?>{}"#, $content);
+    let content = &format!(r#"<?xml version="1.0" encoding="utf-8"?>{}"#, $content);
     assert_eq!(
       data,
       Ok(content.split("\n").map(|s| s.trim()).collect::<String>())