diff --git a/src/rstd.rs b/src/rstd.rs
index 6d9e498..50f78fc 100644
--- a/src/rstd.rs
+++ b/src/rstd.rs
@@ -41,13 +41,11 @@ pub trait SerializableExt: Serializable {
 impl<S: Serializable> SerializableExt for S {}
 
 /// [`ResolverExt::into_rc`].
-pub trait ResolverExt<'a, Ctx: Context<'a>>: Resolver<'a, Ctx> {
+pub trait ResolverExt<'a, Ctx: Context<'a>>: Resolver<'a, Ctx> + Sized {
     /// Wrap the resolver into [`Arc`].
-    fn into_rc(self) -> Arc<dyn Resolver<'a, Ctx>>;
-}
-
-impl<'a, Ctx: Context<'a>, R: Resolver<'a, Ctx>> ResolverExt<'a, Ctx> for R {
     fn into_rc(self) -> Arc<dyn Resolver<'a, Ctx>> {
         Arc::new(self)
     }
 }
+
+impl<'a, Ctx: Context<'a>, R: Resolver<'a, Ctx>> ResolverExt<'a, Ctx> for R {}