diff --git a/substrate/bin/node/runtime/src/lib.rs b/substrate/bin/node/runtime/src/lib.rs
index 7b203d2e93..064132e61c 100644
--- a/substrate/bin/node/runtime/src/lib.rs
+++ b/substrate/bin/node/runtime/src/lib.rs
@@ -82,7 +82,7 @@ pub const VERSION: RuntimeVersion = RuntimeVersion {
 	// and set impl_version to 0. If only runtime
 	// implementation changes and behavior does not, then leave spec_version as
 	// is and increment impl_version.
-	spec_version: 232,
+	spec_version: 233,
 	impl_version: 0,
 	apis: RUNTIME_API_VERSIONS,
 };
diff --git a/substrate/frame/balances/src/migration.rs b/substrate/frame/balances/src/migration.rs
index d50f916b31..4412a38ca1 100644
--- a/substrate/frame/balances/src/migration.rs
+++ b/substrate/frame/balances/src/migration.rs
@@ -68,15 +68,20 @@ fn upgrade_v1_to_v2<T: Trait<I>, I: Instance>() {
 		put_storage_value(b"Balances", b"Account", &hash, account);
 	}
 
+	let prefix = {
+		let encoded_prefix_key_hash = b":session:keys".to_vec().encode();
+		let mut h = twox_64(&encoded_prefix_key_hash[..]).to_vec();
+		h.extend(&encoded_prefix_key_hash[..]);
+		h
+	};
+
 	for (hash, balances) in StorageIterator::<AccountData<T::Balance>>::new(b"Balances", b"Account").drain() {
 		let nonce = take_storage_value::<T::Index>(b"System", b"AccountNonce", &hash).unwrap_or_default();
 		let mut refs: system::RefCount = 0;
 		// The items in Kusama that would result in a ref count being incremented.
 		if have_storage_value(b"Democracy", b"Proxy", &hash) { refs += 1 }
 		// We skip Recovered since it's being replaced anyway.
-		let k = b":session:keys".encode();
-		let mut prefixed_hash = twox_64(&k[..]).to_vec();
-		prefixed_hash.extend(&k[..]);
+		let mut prefixed_hash = prefix.clone();
 		prefixed_hash.extend(&hash[..]);
 		if have_storage_value(b"Session", b"NextKeys", &prefixed_hash) { refs += 1 }
 		if have_storage_value(b"Staking", b"Bonded", &hash) { refs += 1 }