diff --git a/src/backends/plonky2/primitives/ec/schnorr.rs b/src/backends/plonky2/primitives/ec/schnorr.rs
index 054eca6..5e2242e 100644
--- a/src/backends/plonky2/primitives/ec/schnorr.rs
+++ b/src/backends/plonky2/primitives/ec/schnorr.rs
@@ -128,6 +128,7 @@ impl SignatureTarget {
     }
 }
 
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
 pub struct SecretKey(pub BigUint);
 
 impl SecretKey {
diff --git a/src/frontend/error.rs b/src/frontend/error.rs
index e38b740..dc14dfd 100644
--- a/src/frontend/error.rs
+++ b/src/frontend/error.rs
@@ -39,13 +39,17 @@ pub enum Error {
         backtrace: Box<Backtrace>,
     },
     #[error(transparent)]
-    Infallible(#[from] std::convert::Infallible),
-    #[error(transparent)]
     Backend(#[from] BackendError),
     #[error(transparent)]
     Middleware(#[from] crate::middleware::Error),
 }
 
+impl From<std::convert::Infallible> for Error {
+    fn from(value: std::convert::Infallible) -> Self {
+        match value {}
+    }
+}
+
 impl Debug for Error {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         std::fmt::Display::fmt(self, f)
diff --git a/src/frontend/operation.rs b/src/frontend/operation.rs
index abbfbf7..9f7b572 100644
--- a/src/frontend/operation.rs
+++ b/src/frontend/operation.rs
@@ -185,7 +185,7 @@ impl Operation {
     }
     op_impl_oa!(dict_contains, DictContainsFromEntries, 3);
     op_impl_oa!(dict_not_contains, DictNotContainsFromEntries, 2);
-    op_impl_oa!(set_contains, SetContainsFromEntries, 3);
+    op_impl_oa!(set_contains, SetContainsFromEntries, 2);
     op_impl_oa!(set_not_contains, SetNotContainsFromEntries, 2);
     op_impl_oa!(array_contains, ArrayContainsFromEntries, 3);
 }