diff --git a/hugr-core/src/types/signature.rs b/hugr-core/src/types/signature.rs
index c5d3459e1..7578554ce 100644
--- a/hugr-core/src/types/signature.rs
+++ b/hugr-core/src/types/signature.rs
@@ -2,6 +2,7 @@
 
 use itertools::Either;
 
+use std::borrow::Cow;
 use std::fmt::{self, Display, Write};
 
 use super::type_param::TypeParam;
@@ -14,7 +15,7 @@ use crate::extension::{ExtensionRegistry, ExtensionSet, SignatureError};
 use crate::{Direction, IncomingPort, OutgoingPort, Port};
 
 #[cfg(test)]
-use {crate::proptest::RecursionDepth, ::proptest::prelude::*, proptest_derive::Arbitrary};
+use {crate::proptest::RecursionDepth, proptest::prelude::*, proptest_derive::Arbitrary};
 
 #[derive(Clone, Debug, Eq, Hash, serde::Serialize, serde::Deserialize)]
 #[cfg_attr(test, derive(Arbitrary), proptest(params = "RecursionDepth"))]
@@ -319,6 +320,18 @@ impl<RV1: MaybeRV, RV2: MaybeRV> PartialEq<FuncTypeBase<RV1>> for FuncTypeBase<R
     }
 }
 
+impl<RV1: MaybeRV, RV2: MaybeRV> PartialEq<Cow<'_, FuncTypeBase<RV1>>> for FuncTypeBase<RV2> {
+    fn eq(&self, other: &Cow<'_, FuncTypeBase<RV1>>) -> bool {
+        self.eq(other.as_ref())
+    }
+}
+
+impl<RV1: MaybeRV, RV2: MaybeRV> PartialEq<FuncTypeBase<RV1>> for Cow<'_, FuncTypeBase<RV2>> {
+    fn eq(&self, other: &FuncTypeBase<RV1>) -> bool {
+        self.as_ref().eq(other)
+    }
+}
+
 #[cfg(test)]
 mod test {
     use crate::{extension::prelude::usize_t, type_row};