diff --git a/zebra-chain/src/keys/sprout.rs b/zebra-chain/src/keys/sprout.rs
index 2335b4a66..75cefd619 100644
--- a/zebra-chain/src/keys/sprout.rs
+++ b/zebra-chain/src/keys/sprout.rs
@@ -130,6 +130,12 @@ impl From<SpendingKey> for [u8; 32] {
     }
 }
 
+impl<'a> From<&'a SpendingKey> for [u8; 32] {
+    fn from(spending_key: &'a SpendingKey) -> [u8; 32] {
+        spending_key.bytes
+    }
+}
+
 impl std::str::FromStr for SpendingKey {
     type Err = SerializationError;
 
diff --git a/zebra-chain/src/notes/sapling/nullifiers.rs b/zebra-chain/src/notes/sapling/nullifiers.rs
index 836ec712c..37f2590a3 100644
--- a/zebra-chain/src/notes/sapling/nullifiers.rs
+++ b/zebra-chain/src/notes/sapling/nullifiers.rs
@@ -39,8 +39,8 @@ impl From<[u8; 32]> for Nullifier {
     }
 }
 
-impl<'a> From<&'a (NoteCommitment, Position, NullifierDerivingKey)> for Nullifier {
-    fn from((cm, pos, nk): &'a (NoteCommitment, Position, NullifierDerivingKey)) -> Self {
+impl<'a> From<(NoteCommitment, Position, &'a NullifierDerivingKey)> for Nullifier {
+    fn from((cm, pos, nk): (NoteCommitment, Position, &'a NullifierDerivingKey)) -> Self {
         let rho = jubjub::AffinePoint::from(mixing_pedersen_hash(cm.0.into(), pos.0.into()));
 
         Nullifier(prf_nf(nk.into(), rho.to_bytes()))
diff --git a/zebra-chain/src/notes/sprout/nullifiers.rs b/zebra-chain/src/notes/sprout/nullifiers.rs
index 54e647950..8609a8638 100644
--- a/zebra-chain/src/notes/sprout/nullifiers.rs
+++ b/zebra-chain/src/notes/sprout/nullifiers.rs
@@ -73,8 +73,8 @@ impl From<[u8; 32]> for Nullifier {
     }
 }
 
-impl From<(SpendingKey, NullifierSeed)> for Nullifier {
-    fn from((a_sk, rho): (SpendingKey, NullifierSeed)) -> Self {
+impl<'a> From<(&'a SpendingKey, NullifierSeed)> for Nullifier {
+    fn from((a_sk, rho): (&'a SpendingKey, NullifierSeed)) -> Self {
         Self(prf_nf(a_sk.into(), rho.into()))
     }
 }