Added a postfix, see if that fixes the issue

src/main.rs

@@ -100,7 +100,7 @@ mod handlers {
 
         let temperature = locations[location];
 
-        let label = Label::with_value(format!("{}", temperature));
+        let label = Label::with_value(format!("{}", temperature)).set_postfix("foobar");
 
         Ok(warp::reply::json(&label))
     }