fix

barretenberg/cpp/src/barretenberg/vm/avm/trace/trace.cpp

@@ -390,7 +390,8 @@ void AvmTraceBuilder::pay_fee()
     FF current_balance = read_hint.leaf_preimage.value;
 
     const auto updated_balance = current_balance - tx_fee;
-    if (current_balance < tx_fee) {
+    // Comparison on Field gives inverted results, so we cast to uint128, which should be enough for fees.
+    if (static_cast<uint128_t>(current_balance) < static_cast<uint128_t>(tx_fee)) {
         info("Not enough balance for fee payer to pay for transaction (got ", current_balance, " needs ", tx_fee);
         throw std::runtime_error("Not enough balance for fee payer to pay for transaction");
     }