diff --git a/extendr-api/src/io/load.rs b/extendr-api/src/io/load.rs
index e655febe32..f010ef7871 100644
--- a/extendr-api/src/io/load.rs
+++ b/extendr-api/src/io/load.rs
@@ -74,4 +74,4 @@ pub trait Load {
     }
 }
 
-impl Load for Robj {}
+impl<T: ?Sized> Load for T {}
diff --git a/extendr-api/src/io/save.rs b/extendr-api/src/io/save.rs
index a892685d8b..d66449941f 100644
--- a/extendr-api/src/io/save.rs
+++ b/extendr-api/src/io/save.rs
@@ -106,4 +106,4 @@ pub trait Save: GetSexp {
     }
 }
 
-impl<R: GetSexp> Save for R {}
+impl<T: ?Sized + GetSexp> Save for T {}
diff --git a/extendr-api/src/iter.rs b/extendr-api/src/iter.rs
index 6d32e32990..0fa324c18a 100644
--- a/extendr-api/src/iter.rs
+++ b/extendr-api/src/iter.rs
@@ -201,7 +201,7 @@ pub trait AsStrIter: GetSexp + Types + Length + Attributes + Rinternals {
     }
 }
 
-impl AsStrIter for Robj {}
+impl<T: ?Sized + GetSexp + Types + Length + Attributes> AsStrIter for T {}
 
 impl TryFrom<&Robj> for StrIter {
     type Error = Error;
diff --git a/extendr-api/src/robj/mod.rs b/extendr-api/src/robj/mod.rs
index b536c24ab0..d8a8f92b3d 100644
--- a/extendr-api/src/robj/mod.rs
+++ b/extendr-api/src/robj/mod.rs
@@ -760,7 +760,7 @@ pub trait Eval: GetSexp {
     }
 }
 
-impl Eval for Robj {}
+impl<T: ?Sized + GetSexp> Eval for T {}
 
 /// Generic access to typed slices in an Robj.
 pub trait AsTypedSlice<'a, T>
@@ -770,7 +770,9 @@ where
     fn try_into_typed_slice(&self) -> Result<&'a [T]>;
     fn try_into_typed_slice_mut(&mut self) -> Result<&'a mut [T]>;
 
+    #[deprecated]
     fn as_typed_slice(&self) -> Option<&'a [T]>;
+    #[deprecated]
     fn as_typed_slice_mut(&mut self) -> Option<&'a mut [T]>;
 }