diff --git a/components/zcash_protocol/src/memo.rs b/components/zcash_protocol/src/memo.rs
index dafb1bcbe1..10258a52d9 100644
--- a/components/zcash_protocol/src/memo.rs
+++ b/components/zcash_protocol/src/memo.rs
@@ -144,9 +144,10 @@ impl Deref for TextMemo {
 }
 
 /// An unencrypted memo received alongside a shielded note in a Zcash transaction.
-#[derive(Clone)]
+#[derive(Clone, Default)]
 pub enum Memo {
     /// An empty memo field.
+    #[default]
     Empty,
     /// A memo field containing a UTF-8 string.
     Text(TextMemo),
@@ -171,12 +172,6 @@ impl fmt::Debug for Memo {
     }
 }
 
-impl Default for Memo {
-    fn default() -> Self {
-        Memo::Empty
-    }
-}
-
 impl PartialEq for Memo {
     fn eq(&self, rhs: &Memo) -> bool {
         match (self, rhs) {
diff --git a/zcash_primitives/src/transaction/sighash.rs b/zcash_primitives/src/transaction/sighash.rs
index 702ed17575..4be0a7454b 100644
--- a/zcash_primitives/src/transaction/sighash.rs
+++ b/zcash_primitives/src/transaction/sighash.rs
@@ -76,13 +76,12 @@ pub trait TransparentAuthorizingContext: transparent::Authorization {
 /// set of precomputed hashes produced in the construction of the
 /// transaction ID.
 pub fn signature_hash<
-    'a,
     TA: TransparentAuthorizingContext,
     SA: sapling::bundle::Authorization<SpendProof = GrothProofBytes, OutputProof = GrothProofBytes>,
     A: Authorization<SaplingAuth = SA, TransparentAuth = TA>,
 >(
     tx: &TransactionData<A>,
-    signable_input: &SignableInput<'a>,
+    signable_input: &SignableInput<'_>,
     txid_parts: &TxDigests<Blake2bHash>,
 ) -> SignatureHash {
     SignatureHash(match tx.version {
diff --git a/zcash_proofs/src/circuit/sprout/input.rs b/zcash_proofs/src/circuit/sprout/input.rs
index 39a2d4170a..cadcfcbd8c 100644
--- a/zcash_proofs/src/circuit/sprout/input.rs
+++ b/zcash_proofs/src/circuit/sprout/input.rs
@@ -66,7 +66,7 @@ impl InputNote {
             let lhs = cur;
             let rhs = witness_u256(
                 cs.namespace(|| "sibling"),
-                layer.as_ref().map(|&(ref sibling, _)| &sibling[..]),
+                layer.as_ref().map(|(sibling, _)| &sibling[..]),
             )?;
 
             // Conditionally swap if cur is right