diff --git a/viz-core/tests/handler.rs b/viz-core/tests/handler.rs
index 10e7d60..48c566e 100644
--- a/viz-core/tests/handler.rs
+++ b/viz-core/tests/handler.rs
@@ -162,7 +162,7 @@ async fn handler() -> Result<()> {
         type Output = Result<I>;
 
         async fn call(&self, i: I) -> Self::Output {
-            Ok(i)
+            Ok::<I, _>(i)
         }
     }
 
@@ -235,7 +235,9 @@ async fn handler() -> Result<()> {
         )
         .catch_unwind(|_: Box<dyn std::any::Any + Send>| async move { panic!("Custom Error 2") });
 
-    assert!(Handler::call(&aa, Request::new(Body::Empty)).await.is_ok());
+    #[allow(dependency_on_unit_never_type_fallback)]
+    let resp: Result<Response> = aa.call(Request::new(Body::Empty)).await;
+    assert!(resp.is_ok());
 
     let th = MyAround {
         name: String::new(),