diff --git a/transaction-view/src/resolved_transaction_view.rs b/transaction-view/src/resolved_transaction_view.rs
index 8fe2c5c12354fe..1bc8cd1ef8508b 100644
--- a/transaction-view/src/resolved_transaction_view.rs
+++ b/transaction-view/src/resolved_transaction_view.rs
@@ -32,6 +32,8 @@ pub struct ResolvedTransactionView<D: TransactionData> {
     /// The resolved address lookups.
     resolved_addresses: Option<LoadedAddresses>,
     /// A cache for whether an address is writable.
+    // Sanitized transactions are guaranteed to have a maximum of 256 keys,
+    // because account indexing is done with a u8.
     writable_cache: [bool; 256],
 }