diff --git a/serde_derive/src/de.rs b/serde_derive/src/de.rs
index aedbf332..05b952aa 100644
--- a/serde_derive/src/de.rs
+++ b/serde_derive/src/de.rs
@@ -1428,7 +1428,7 @@ fn deserialize_identifier(
                     #variant_indices => _serde::export::Ok(#constructors),
                 )*
                 _ => _serde::export::Err(_serde::de::Error::invalid_value(
-                            _serde::de::Unexpected::Unsigned(__value as u64),
+                            _serde::de::Unexpected::Unsigned(__value),
                             &#fallthrough_msg))
             }
         }
diff --git a/test_suite/tests/test_macros.rs b/test_suite/tests/test_macros.rs
index f2b478e8..66e72f23 100644
--- a/test_suite/tests/test_macros.rs
+++ b/test_suite/tests/test_macros.rs
@@ -6,6 +6,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![deny(trivial_numeric_casts)]
+
 #[macro_use]
 extern crate serde_derive;