diff --git a/iri/src/lib.rs b/iri/src/lib.rs
index 4cd77ee7..1c81ed89 100644
--- a/iri/src/lib.rs
+++ b/iri/src/lib.rs
@@ -48,4 +48,4 @@ pub use ThreadSafeError as Error;
 
 /// An error trait meant to enable sending errors safely across threads.
 pub trait ThreadSafeError: std::error::Error + Send + Sync + 'static {}
-impl<E> ThreadSafeError for E where E: std::error::Error + Send + Sync + 'static + ?Sized {}
+impl<E> ThreadSafeError for E where E: std::error::Error + Send + Sync + 'static {}