diff --git a/README.md b/README.md
index 6c98cf1..fa257b8 100644
--- a/README.md
+++ b/README.md
@@ -143,11 +143,10 @@ trait Visitor {
 - ✓ Support for traits with generic arguments.
 - ✓ `#[derive(Ref)]`
 - ✓ `#[derive(Mut)]`
-- ✓ `#[derive(Box)]`
+- ✓ `#[derive(Box)]` for both sized and unsized types.
 - ✓ `#[derive(Rc)]`
 - ✓ `#[derive(Arc)]`
-- ✗ Update `Box` derive to allow unsized types if possible.
-- ✗ `#[derive(Cow)]`
+- ✓ `#[derive(Cow)]`
 
 ## 🤝 Credits
 
diff --git a/tests/derive_arc/successes/async_assoc_function.rs b/tests/derive_arc/successes/async_assoc_function.rs
new file mode 100644
index 0000000..336110a
--- /dev/null
+++ b/tests/derive_arc/successes/async_assoc_function.rs
@@ -0,0 +1,20 @@
+use std::sync::Arc;
+
+use impls::impls;
+
+#[blanket::blanket(derive(Arc))]
+trait Foo {
+    async fn bar();
+}
+
+#[derive(Default)]
+struct Baz;
+
+impl Foo for Baz {
+    async fn bar() {}
+}
+
+fn main() {
+    assert!(impls!(Baz:  Foo));
+    assert!(impls!(Arc<Baz>: Foo));
+}
\ No newline at end of file
diff --git a/tests/derive_arc/successes/async_method.rs b/tests/derive_arc/successes/async_method.rs
new file mode 100644
index 0000000..33bde28
--- /dev/null
+++ b/tests/derive_arc/successes/async_method.rs
@@ -0,0 +1,20 @@
+use std::sync::Arc;
+
+use impls::impls;
+
+#[blanket::blanket(derive(Arc))]
+trait Foo {
+    async fn bar(&self);
+}
+
+#[derive(Default)]
+struct Baz;
+
+impl Foo for Baz {
+    async fn bar(&self) {}
+}
+
+fn main() {
+    assert!(impls!(Baz:  Foo));
+    assert!(impls!(Arc<Baz>: Foo));
+}
\ No newline at end of file
diff --git a/tests/derive_box/successes/async_assoc_function.rs b/tests/derive_box/successes/async_assoc_function.rs
new file mode 100644
index 0000000..aeaab17
--- /dev/null
+++ b/tests/derive_box/successes/async_assoc_function.rs
@@ -0,0 +1,18 @@
+use impls::impls;
+
+#[blanket::blanket(derive(Box))]
+trait Foo {
+    async fn bar();
+}
+
+#[derive(Default)]
+struct Baz;
+
+impl Foo for Baz {
+    async fn bar() {}
+}
+
+fn main() {
+    assert!(impls!(Baz:  Foo));
+    assert!(impls!(Box<Baz>: Foo));
+}
\ No newline at end of file
diff --git a/tests/derive_box/successes/async_method.rs b/tests/derive_box/successes/async_method.rs
new file mode 100644
index 0000000..d08d0d8
--- /dev/null
+++ b/tests/derive_box/successes/async_method.rs
@@ -0,0 +1,18 @@
+use impls::impls;
+
+#[blanket::blanket(derive(Box))]
+trait Foo {
+    async fn bar(&self);
+}
+
+#[derive(Default)]
+struct Baz;
+
+impl Foo for Baz {
+    async fn bar(&self) {}
+}
+
+fn main() {
+    assert!(impls!(Baz:  Foo));
+    assert!(impls!(Box<Baz>: Foo));
+}
\ No newline at end of file
diff --git a/tests/derive_cow/successes/async_assoc_function.rs b/tests/derive_cow/successes/async_assoc_function.rs
new file mode 100644
index 0000000..2316fb9
--- /dev/null
+++ b/tests/derive_cow/successes/async_assoc_function.rs
@@ -0,0 +1,20 @@
+use std::borrow::Cow;
+
+use impls::impls;
+
+#[blanket::blanket(derive(Cow))]
+trait Foo {
+    async fn bar();
+}
+
+#[derive(Default, Clone)]
+struct Baz;
+
+impl Foo for Baz {
+    async fn bar() {}
+}
+
+fn main() {
+    assert!(impls!(Baz:  Foo));
+    assert!(impls!(Cow<Baz>: Foo));
+}
\ No newline at end of file
diff --git a/tests/derive_cow/successes/async_method.rs b/tests/derive_cow/successes/async_method.rs
new file mode 100644
index 0000000..92a0010
--- /dev/null
+++ b/tests/derive_cow/successes/async_method.rs
@@ -0,0 +1,20 @@
+use std::borrow::Cow;
+
+use impls::impls;
+
+#[blanket::blanket(derive(Cow))]
+trait Foo {
+    async fn bar(&self);
+}
+
+#[derive(Default, Clone)]
+struct Baz;
+
+impl Foo for Baz {
+    async fn bar(&self) {}
+}
+
+fn main() {
+    assert!(impls!(Baz:  Foo));
+    assert!(impls!(Cow<Baz>: Foo));
+}
\ No newline at end of file
diff --git a/tests/derive_rc/successes/async_assoc_function.rs b/tests/derive_rc/successes/async_assoc_function.rs
new file mode 100644
index 0000000..b9c9833
--- /dev/null
+++ b/tests/derive_rc/successes/async_assoc_function.rs
@@ -0,0 +1,20 @@
+use std::rc::Rc;
+
+use impls::impls;
+
+#[blanket::blanket(derive(Rc))]
+trait Foo {
+    async fn bar();
+}
+
+#[derive(Default)]
+struct Baz;
+
+impl Foo for Baz {
+    async fn bar() {}
+}
+
+fn main() {
+    assert!(impls!(Baz:  Foo));
+    assert!(impls!(Rc<Baz>: Foo));
+}
\ No newline at end of file
diff --git a/tests/derive_rc/successes/async_method.rs b/tests/derive_rc/successes/async_method.rs
new file mode 100644
index 0000000..b41a396
--- /dev/null
+++ b/tests/derive_rc/successes/async_method.rs
@@ -0,0 +1,20 @@
+use std::rc::Rc;
+
+use impls::impls;
+
+#[blanket::blanket(derive(Rc))]
+trait Foo {
+    async fn bar(&self);
+}
+
+#[derive(Default)]
+struct Baz;
+
+impl Foo for Baz {
+    async fn bar(&self) {}
+}
+
+fn main() {
+    assert!(impls!(Baz:  Foo));
+    assert!(impls!(Rc<Baz>: Foo));
+}
\ No newline at end of file
diff --git a/tests/derive_ref/successes/async_assoc_function.rs b/tests/derive_ref/successes/async_assoc_function.rs
new file mode 100644
index 0000000..118c0bd
--- /dev/null
+++ b/tests/derive_ref/successes/async_assoc_function.rs
@@ -0,0 +1,18 @@
+use impls::impls;
+
+#[blanket::blanket(derive(Ref))]
+trait Foo {
+    async fn bar();
+}
+
+#[derive(Default)]
+struct Baz;
+
+impl Foo for Baz {
+    async fn bar() {}
+}
+
+fn main() {
+    assert!(impls!(Baz:  Foo));
+    assert!(impls!(&Baz: Foo));
+}
\ No newline at end of file
diff --git a/tests/derive_ref/successes/async_method.rs b/tests/derive_ref/successes/async_method.rs
new file mode 100644
index 0000000..3903059
--- /dev/null
+++ b/tests/derive_ref/successes/async_method.rs
@@ -0,0 +1,18 @@
+use impls::impls;
+
+#[blanket::blanket(derive(Ref))]
+trait Foo {
+    async fn bar(&self);
+}
+
+#[derive(Default)]
+struct Baz;
+
+impl Foo for Baz {
+    async fn bar(&self) {}
+}
+
+fn main() {
+    assert!(impls!(Baz:  Foo));
+    assert!(impls!(&Baz: Foo));
+}
\ No newline at end of file