diff --git a/src/ethereum/arrow_glacier/transactions.py b/src/ethereum/arrow_glacier/transactions.py
index d11bc88219..c31fa26063 100644
--- a/src/ethereum/arrow_glacier/transactions.py
+++ b/src/ethereum/arrow_glacier/transactions.py
@@ -34,7 +34,7 @@ class LegacyTransaction:
     Atomic operation performed on the block chain.
     """
 
-    nonce: U256
+    nonce: U64
     gas_price: Uint
     gas: Uint
     to: Union[Bytes0, Address]
@@ -53,7 +53,7 @@ class AccessListTransaction:
     """
 
     chain_id: U64
-    nonce: U256
+    nonce: U64
     gas_price: Uint
     gas: Uint
     to: Union[Bytes0, Address]
@@ -73,7 +73,7 @@ class FeeMarketTransaction:
     """
 
     chain_id: U64
-    nonce: U256
+    nonce: U64
     max_priority_fee_per_gas: Uint
     max_fee_per_gas: Uint
     gas: Uint
diff --git a/src/ethereum/berlin/transactions.py b/src/ethereum/berlin/transactions.py
index 19994de100..f23d86e98b 100644
--- a/src/ethereum/berlin/transactions.py
+++ b/src/ethereum/berlin/transactions.py
@@ -34,7 +34,7 @@ class LegacyTransaction:
     Atomic operation performed on the block chain.
     """
 
-    nonce: U256
+    nonce: U64
     gas_price: Uint
     gas: Uint
     to: Union[Bytes0, Address]
@@ -53,7 +53,7 @@ class AccessListTransaction:
     """
 
     chain_id: U64
-    nonce: U256
+    nonce: U64
     gas_price: Uint
     gas: Uint
     to: Union[Bytes0, Address]
diff --git a/src/ethereum/byzantium/transactions.py b/src/ethereum/byzantium/transactions.py
index 99c55fc975..2dd74c7961 100644
--- a/src/ethereum/byzantium/transactions.py
+++ b/src/ethereum/byzantium/transactions.py
@@ -6,7 +6,7 @@
 from dataclasses import dataclass
 from typing import Union
 
-from ..base_types import U256, Bytes, Bytes0, Uint, slotted_freezable
+from ..base_types import U64, U256, Bytes, Bytes0, Uint, slotted_freezable
 from .fork_types import Address
 
 TX_BASE_COST = 21000
@@ -22,7 +22,7 @@ class Transaction:
     Atomic operation performed on the block chain.
     """
 
-    nonce: U256
+    nonce: U64
     gas_price: Uint
     gas: Uint
     to: Union[Bytes0, Address]
diff --git a/src/ethereum/cancun/transactions.py b/src/ethereum/cancun/transactions.py
index d81d11ed13..cfdebb453c 100644
--- a/src/ethereum/cancun/transactions.py
+++ b/src/ethereum/cancun/transactions.py
@@ -34,7 +34,7 @@ class LegacyTransaction:
     Atomic operation performed on the block chain.
     """
 
-    nonce: U256
+    nonce: U64
     gas_price: Uint
     gas: Uint
     to: Union[Bytes0, Address]
@@ -53,7 +53,7 @@ class AccessListTransaction:
     """
 
     chain_id: U64
-    nonce: U256
+    nonce: U64
     gas_price: Uint
     gas: Uint
     to: Union[Bytes0, Address]
@@ -73,7 +73,7 @@ class FeeMarketTransaction:
     """
 
     chain_id: U64
-    nonce: U256
+    nonce: U64
     max_priority_fee_per_gas: Uint
     max_fee_per_gas: Uint
     gas: Uint
@@ -94,7 +94,7 @@ class BlobTransaction:
     """
 
     chain_id: U64
-    nonce: U256
+    nonce: U64
     max_priority_fee_per_gas: Uint
     max_fee_per_gas: Uint
     gas: Uint
diff --git a/src/ethereum/constantinople/transactions.py b/src/ethereum/constantinople/transactions.py
index 99c55fc975..2dd74c7961 100644
--- a/src/ethereum/constantinople/transactions.py
+++ b/src/ethereum/constantinople/transactions.py
@@ -6,7 +6,7 @@
 from dataclasses import dataclass
 from typing import Union
 
-from ..base_types import U256, Bytes, Bytes0, Uint, slotted_freezable
+from ..base_types import U64, U256, Bytes, Bytes0, Uint, slotted_freezable
 from .fork_types import Address
 
 TX_BASE_COST = 21000
@@ -22,7 +22,7 @@ class Transaction:
     Atomic operation performed on the block chain.
     """
 
-    nonce: U256
+    nonce: U64
     gas_price: Uint
     gas: Uint
     to: Union[Bytes0, Address]
diff --git a/src/ethereum/dao_fork/transactions.py b/src/ethereum/dao_fork/transactions.py
index 99c55fc975..2dd74c7961 100644
--- a/src/ethereum/dao_fork/transactions.py
+++ b/src/ethereum/dao_fork/transactions.py
@@ -6,7 +6,7 @@
 from dataclasses import dataclass
 from typing import Union
 
-from ..base_types import U256, Bytes, Bytes0, Uint, slotted_freezable
+from ..base_types import U64, U256, Bytes, Bytes0, Uint, slotted_freezable
 from .fork_types import Address
 
 TX_BASE_COST = 21000
@@ -22,7 +22,7 @@ class Transaction:
     Atomic operation performed on the block chain.
     """
 
-    nonce: U256
+    nonce: U64
     gas_price: Uint
     gas: Uint
     to: Union[Bytes0, Address]
diff --git a/src/ethereum/frontier/transactions.py b/src/ethereum/frontier/transactions.py
index a08b4cf71d..afa9731903 100644
--- a/src/ethereum/frontier/transactions.py
+++ b/src/ethereum/frontier/transactions.py
@@ -6,7 +6,7 @@
 from dataclasses import dataclass
 from typing import Union
 
-from ..base_types import U256, Bytes, Bytes0, Uint, slotted_freezable
+from ..base_types import U64, U256, Bytes, Bytes0, Uint, slotted_freezable
 from .fork_types import Address
 
 TX_BASE_COST = 21000
@@ -21,7 +21,7 @@ class Transaction:
     Atomic operation performed on the block chain.
     """
 
-    nonce: U256
+    nonce: U64
     gas_price: Uint
     gas: Uint
     to: Union[Bytes0, Address]
diff --git a/src/ethereum/gray_glacier/transactions.py b/src/ethereum/gray_glacier/transactions.py
index d11bc88219..c31fa26063 100644
--- a/src/ethereum/gray_glacier/transactions.py
+++ b/src/ethereum/gray_glacier/transactions.py
@@ -34,7 +34,7 @@ class LegacyTransaction:
     Atomic operation performed on the block chain.
     """
 
-    nonce: U256
+    nonce: U64
     gas_price: Uint
     gas: Uint
     to: Union[Bytes0, Address]
@@ -53,7 +53,7 @@ class AccessListTransaction:
     """
 
     chain_id: U64
-    nonce: U256
+    nonce: U64
     gas_price: Uint
     gas: Uint
     to: Union[Bytes0, Address]
@@ -73,7 +73,7 @@ class FeeMarketTransaction:
     """
 
     chain_id: U64
-    nonce: U256
+    nonce: U64
     max_priority_fee_per_gas: Uint
     max_fee_per_gas: Uint
     gas: Uint
diff --git a/src/ethereum/homestead/transactions.py b/src/ethereum/homestead/transactions.py
index 99c55fc975..2dd74c7961 100644
--- a/src/ethereum/homestead/transactions.py
+++ b/src/ethereum/homestead/transactions.py
@@ -6,7 +6,7 @@
 from dataclasses import dataclass
 from typing import Union
 
-from ..base_types import U256, Bytes, Bytes0, Uint, slotted_freezable
+from ..base_types import U64, U256, Bytes, Bytes0, Uint, slotted_freezable
 from .fork_types import Address
 
 TX_BASE_COST = 21000
@@ -22,7 +22,7 @@ class Transaction:
     Atomic operation performed on the block chain.
     """
 
-    nonce: U256
+    nonce: U64
     gas_price: Uint
     gas: Uint
     to: Union[Bytes0, Address]
diff --git a/src/ethereum/istanbul/transactions.py b/src/ethereum/istanbul/transactions.py
index af0c75abf8..9f356527c5 100644
--- a/src/ethereum/istanbul/transactions.py
+++ b/src/ethereum/istanbul/transactions.py
@@ -6,7 +6,7 @@
 from dataclasses import dataclass
 from typing import Union
 
-from ..base_types import U256, Bytes, Bytes0, Uint, slotted_freezable
+from ..base_types import U64, U256, Bytes, Bytes0, Uint, slotted_freezable
 from .fork_types import Address
 
 TX_BASE_COST = 21000
@@ -22,7 +22,7 @@ class Transaction:
     Atomic operation performed on the block chain.
     """
 
-    nonce: U256
+    nonce: U64
     gas_price: Uint
     gas: Uint
     to: Union[Bytes0, Address]
diff --git a/src/ethereum/london/transactions.py b/src/ethereum/london/transactions.py
index d11bc88219..c31fa26063 100644
--- a/src/ethereum/london/transactions.py
+++ b/src/ethereum/london/transactions.py
@@ -34,7 +34,7 @@ class LegacyTransaction:
     Atomic operation performed on the block chain.
     """
 
-    nonce: U256
+    nonce: U64
     gas_price: Uint
     gas: Uint
     to: Union[Bytes0, Address]
@@ -53,7 +53,7 @@ class AccessListTransaction:
     """
 
     chain_id: U64
-    nonce: U256
+    nonce: U64
     gas_price: Uint
     gas: Uint
     to: Union[Bytes0, Address]
@@ -73,7 +73,7 @@ class FeeMarketTransaction:
     """
 
     chain_id: U64
-    nonce: U256
+    nonce: U64
     max_priority_fee_per_gas: Uint
     max_fee_per_gas: Uint
     gas: Uint
diff --git a/src/ethereum/muir_glacier/transactions.py b/src/ethereum/muir_glacier/transactions.py
index af0c75abf8..9f356527c5 100644
--- a/src/ethereum/muir_glacier/transactions.py
+++ b/src/ethereum/muir_glacier/transactions.py
@@ -6,7 +6,7 @@
 from dataclasses import dataclass
 from typing import Union
 
-from ..base_types import U256, Bytes, Bytes0, Uint, slotted_freezable
+from ..base_types import U64, U256, Bytes, Bytes0, Uint, slotted_freezable
 from .fork_types import Address
 
 TX_BASE_COST = 21000
@@ -22,7 +22,7 @@ class Transaction:
     Atomic operation performed on the block chain.
     """
 
-    nonce: U256
+    nonce: U64
     gas_price: Uint
     gas: Uint
     to: Union[Bytes0, Address]
diff --git a/src/ethereum/paris/transactions.py b/src/ethereum/paris/transactions.py
index d11bc88219..c31fa26063 100644
--- a/src/ethereum/paris/transactions.py
+++ b/src/ethereum/paris/transactions.py
@@ -34,7 +34,7 @@ class LegacyTransaction:
     Atomic operation performed on the block chain.
     """
 
-    nonce: U256
+    nonce: U64
     gas_price: Uint
     gas: Uint
     to: Union[Bytes0, Address]
@@ -53,7 +53,7 @@ class AccessListTransaction:
     """
 
     chain_id: U64
-    nonce: U256
+    nonce: U64
     gas_price: Uint
     gas: Uint
     to: Union[Bytes0, Address]
@@ -73,7 +73,7 @@ class FeeMarketTransaction:
     """
 
     chain_id: U64
-    nonce: U256
+    nonce: U64
     max_priority_fee_per_gas: Uint
     max_fee_per_gas: Uint
     gas: Uint
diff --git a/src/ethereum/shanghai/transactions.py b/src/ethereum/shanghai/transactions.py
index d11bc88219..c31fa26063 100644
--- a/src/ethereum/shanghai/transactions.py
+++ b/src/ethereum/shanghai/transactions.py
@@ -34,7 +34,7 @@ class LegacyTransaction:
     Atomic operation performed on the block chain.
     """
 
-    nonce: U256
+    nonce: U64
     gas_price: Uint
     gas: Uint
     to: Union[Bytes0, Address]
@@ -53,7 +53,7 @@ class AccessListTransaction:
     """
 
     chain_id: U64
-    nonce: U256
+    nonce: U64
     gas_price: Uint
     gas: Uint
     to: Union[Bytes0, Address]
@@ -73,7 +73,7 @@ class FeeMarketTransaction:
     """
 
     chain_id: U64
-    nonce: U256
+    nonce: U64
     max_priority_fee_per_gas: Uint
     max_fee_per_gas: Uint
     gas: Uint
diff --git a/src/ethereum/spurious_dragon/transactions.py b/src/ethereum/spurious_dragon/transactions.py
index 99c55fc975..2dd74c7961 100644
--- a/src/ethereum/spurious_dragon/transactions.py
+++ b/src/ethereum/spurious_dragon/transactions.py
@@ -6,7 +6,7 @@
 from dataclasses import dataclass
 from typing import Union
 
-from ..base_types import U256, Bytes, Bytes0, Uint, slotted_freezable
+from ..base_types import U64, U256, Bytes, Bytes0, Uint, slotted_freezable
 from .fork_types import Address
 
 TX_BASE_COST = 21000
@@ -22,7 +22,7 @@ class Transaction:
     Atomic operation performed on the block chain.
     """
 
-    nonce: U256
+    nonce: U64
     gas_price: Uint
     gas: Uint
     to: Union[Bytes0, Address]
diff --git a/src/ethereum/tangerine_whistle/transactions.py b/src/ethereum/tangerine_whistle/transactions.py
index 99c55fc975..2dd74c7961 100644
--- a/src/ethereum/tangerine_whistle/transactions.py
+++ b/src/ethereum/tangerine_whistle/transactions.py
@@ -6,7 +6,7 @@
 from dataclasses import dataclass
 from typing import Union
 
-from ..base_types import U256, Bytes, Bytes0, Uint, slotted_freezable
+from ..base_types import U64, U256, Bytes, Bytes0, Uint, slotted_freezable
 from .fork_types import Address
 
 TX_BASE_COST = 21000
@@ -22,7 +22,7 @@ class Transaction:
     Atomic operation performed on the block chain.
     """
 
-    nonce: U256
+    nonce: U64
     gas_price: Uint
     gas: Uint
     to: Union[Bytes0, Address]
diff --git a/tests/berlin/test_rlp.py b/tests/berlin/test_rlp.py
index b1d7e4e4b7..bf7f9b647a 100644
--- a/tests/berlin/test_rlp.py
+++ b/tests/berlin/test_rlp.py
@@ -39,7 +39,7 @@
 )
 
 legacy_transaction = LegacyTransaction(
-    U256(1),
+    U64(1),
     Uint(2),
     Uint(3),
     Bytes0(),
@@ -52,7 +52,7 @@
 
 access_list_transaction = AccessListTransaction(
     U64(1),
-    U256(1),
+    U64(1),
     Uint(2),
     Uint(3),
     Bytes0(),
diff --git a/tests/byzantium/test_rlp.py b/tests/byzantium/test_rlp.py
index bbce187093..0ea1082433 100644
--- a/tests/byzantium/test_rlp.py
+++ b/tests/byzantium/test_rlp.py
@@ -1,7 +1,7 @@
 import pytest
 
 import ethereum.rlp as rlp
-from ethereum.base_types import U256, Bytes, Bytes0, Bytes8, Uint
+from ethereum.base_types import U64, U256, Bytes, Bytes0, Bytes8, Uint
 from ethereum.byzantium.blocks import Block, Header, Log, Receipt
 from ethereum.byzantium.transactions import Transaction
 from ethereum.byzantium.utils.hexadecimal import hex_to_address
@@ -33,7 +33,7 @@
 )
 
 transaction1 = Transaction(
-    U256(1),
+    U64(1),
     Uint(2),
     Uint(3),
     Bytes0(),
@@ -45,7 +45,7 @@
 )
 
 transaction2 = Transaction(
-    U256(1),
+    U64(1),
     Uint(2),
     Uint(3),
     Bytes0(),
diff --git a/tests/cancun/test_rlp.py b/tests/cancun/test_rlp.py
index 747eeb7e48..23a39a1c07 100644
--- a/tests/cancun/test_rlp.py
+++ b/tests/cancun/test_rlp.py
@@ -40,7 +40,7 @@
 )
 
 legacy_transaction = LegacyTransaction(
-    U256(1),
+    U64(1),
     Uint(2),
     Uint(3),
     Bytes0(),
@@ -53,7 +53,7 @@
 
 access_list_transaction = AccessListTransaction(
     U64(1),
-    U256(1),
+    U64(1),
     Uint(2),
     Uint(3),
     Bytes0(),
@@ -67,7 +67,7 @@
 
 transaction_1559 = FeeMarketTransaction(
     U64(1),
-    U256(1),
+    U64(1),
     Uint(7),
     Uint(2),
     Uint(3),
diff --git a/tests/constantinople/test_rlp.py b/tests/constantinople/test_rlp.py
index 198d8c1dad..738404bdf7 100644
--- a/tests/constantinople/test_rlp.py
+++ b/tests/constantinople/test_rlp.py
@@ -1,7 +1,7 @@
 import pytest
 
 import ethereum.rlp as rlp
-from ethereum.base_types import U256, Bytes, Bytes0, Bytes8, Uint
+from ethereum.base_types import U64, U256, Bytes, Bytes0, Bytes8, Uint
 from ethereum.constantinople.blocks import Block, Header, Log, Receipt
 from ethereum.constantinople.transactions import Transaction
 from ethereum.constantinople.utils.hexadecimal import hex_to_address
@@ -33,7 +33,7 @@
 )
 
 transaction1 = Transaction(
-    U256(1),
+    U64(1),
     Uint(2),
     Uint(3),
     Bytes0(),
@@ -45,7 +45,7 @@
 )
 
 transaction2 = Transaction(
-    U256(1),
+    U64(1),
     Uint(2),
     Uint(3),
     Bytes0(),
diff --git a/tests/frontier/test_rlp.py b/tests/frontier/test_rlp.py
index 432d3c03ad..495d721a07 100644
--- a/tests/frontier/test_rlp.py
+++ b/tests/frontier/test_rlp.py
@@ -1,7 +1,7 @@
 import pytest
 
 import ethereum.rlp as rlp
-from ethereum.base_types import U256, Bytes, Bytes0, Bytes8, Uint
+from ethereum.base_types import U64, U256, Bytes, Bytes0, Bytes8, Uint
 from ethereum.crypto.hash import keccak256
 from ethereum.frontier.blocks import Block, Header, Log, Receipt
 from ethereum.frontier.transactions import Transaction
@@ -33,7 +33,7 @@
 )
 
 transaction1 = Transaction(
-    U256(1),
+    U64(1),
     Uint(2),
     Uint(3),
     Bytes0(),
@@ -45,7 +45,7 @@
 )
 
 transaction2 = Transaction(
-    U256(1),
+    U64(1),
     Uint(2),
     Uint(3),
     Bytes0(),
diff --git a/tests/homestead/test_rlp.py b/tests/homestead/test_rlp.py
index e73ccec886..c8b398597c 100644
--- a/tests/homestead/test_rlp.py
+++ b/tests/homestead/test_rlp.py
@@ -1,7 +1,7 @@
 import pytest
 
 import ethereum.rlp as rlp
-from ethereum.base_types import U256, Bytes, Bytes0, Bytes8, Uint
+from ethereum.base_types import U64, U256, Bytes, Bytes0, Bytes8, Uint
 from ethereum.crypto.hash import keccak256
 from ethereum.homestead.blocks import Block, Header, Log, Receipt
 from ethereum.homestead.transactions import Transaction
@@ -33,7 +33,7 @@
 )
 
 transaction1 = Transaction(
-    U256(1),
+    U64(1),
     Uint(2),
     Uint(3),
     Bytes0(),
@@ -45,7 +45,7 @@
 )
 
 transaction2 = Transaction(
-    U256(1),
+    U64(1),
     Uint(2),
     Uint(3),
     Bytes0(),
diff --git a/tests/istanbul/test_rlp.py b/tests/istanbul/test_rlp.py
index 992c7762f0..4ec0afbdc1 100644
--- a/tests/istanbul/test_rlp.py
+++ b/tests/istanbul/test_rlp.py
@@ -1,7 +1,7 @@
 import pytest
 
 import ethereum.rlp as rlp
-from ethereum.base_types import U256, Bytes, Bytes0, Bytes8, Uint
+from ethereum.base_types import U64, U256, Bytes, Bytes0, Bytes8, Uint
 from ethereum.crypto.hash import keccak256
 from ethereum.istanbul.blocks import Block, Header, Log, Receipt
 from ethereum.istanbul.transactions import Transaction
@@ -33,7 +33,7 @@
 )
 
 transaction1 = Transaction(
-    U256(1),
+    U64(1),
     Uint(2),
     Uint(3),
     Bytes0(),
@@ -45,7 +45,7 @@
 )
 
 transaction2 = Transaction(
-    U256(1),
+    U64(1),
     Uint(2),
     Uint(3),
     Bytes0(),
diff --git a/tests/london/test_rlp.py b/tests/london/test_rlp.py
index 56f6a4f81c..7be8d159f0 100644
--- a/tests/london/test_rlp.py
+++ b/tests/london/test_rlp.py
@@ -40,7 +40,7 @@
 )
 
 legacy_transaction = LegacyTransaction(
-    U256(1),
+    U64(1),
     Uint(2),
     Uint(3),
     Bytes0(),
@@ -53,7 +53,7 @@
 
 access_list_transaction = AccessListTransaction(
     U64(1),
-    U256(1),
+    U64(1),
     Uint(2),
     Uint(3),
     Bytes0(),
@@ -67,7 +67,7 @@
 
 transaction_1559 = FeeMarketTransaction(
     U64(1),
-    U256(1),
+    U64(1),
     Uint(7),
     Uint(2),
     Uint(3),
diff --git a/tests/paris/test_rlp.py b/tests/paris/test_rlp.py
index 695f385bd4..acfc87cc3f 100644
--- a/tests/paris/test_rlp.py
+++ b/tests/paris/test_rlp.py
@@ -40,7 +40,7 @@
 )
 
 legacy_transaction = LegacyTransaction(
-    U256(1),
+    U64(1),
     Uint(2),
     Uint(3),
     Bytes0(),
@@ -53,7 +53,7 @@
 
 access_list_transaction = AccessListTransaction(
     U64(1),
-    U256(1),
+    U64(1),
     Uint(2),
     Uint(3),
     Bytes0(),
@@ -67,7 +67,7 @@
 
 transaction_1559 = FeeMarketTransaction(
     U64(1),
-    U256(1),
+    U64(1),
     Uint(7),
     Uint(2),
     Uint(3),
diff --git a/tests/shanghai/test_rlp.py b/tests/shanghai/test_rlp.py
index 2b073783c5..2b7b4824e8 100644
--- a/tests/shanghai/test_rlp.py
+++ b/tests/shanghai/test_rlp.py
@@ -40,7 +40,7 @@
 )
 
 legacy_transaction = LegacyTransaction(
-    U256(1),
+    U64(1),
     Uint(2),
     Uint(3),
     Bytes0(),
@@ -53,7 +53,7 @@
 
 access_list_transaction = AccessListTransaction(
     U64(1),
-    U256(1),
+    U64(1),
     Uint(2),
     Uint(3),
     Bytes0(),
@@ -67,7 +67,7 @@
 
 transaction_1559 = FeeMarketTransaction(
     U64(1),
-    U256(1),
+    U64(1),
     Uint(7),
     Uint(2),
     Uint(3),
diff --git a/tests/spurious_dragon/test_rlp.py b/tests/spurious_dragon/test_rlp.py
index d57e640292..15f10c474f 100644
--- a/tests/spurious_dragon/test_rlp.py
+++ b/tests/spurious_dragon/test_rlp.py
@@ -1,7 +1,7 @@
 import pytest
 
 import ethereum.rlp as rlp
-from ethereum.base_types import U256, Bytes, Bytes0, Bytes8, Uint
+from ethereum.base_types import U64, U256, Bytes, Bytes0, Bytes8, Uint
 from ethereum.crypto.hash import keccak256
 from ethereum.spurious_dragon.blocks import Block, Header, Log, Receipt
 from ethereum.spurious_dragon.transactions import Transaction
@@ -33,7 +33,7 @@
 )
 
 transaction1 = Transaction(
-    U256(1),
+    U64(1),
     Uint(2),
     Uint(3),
     Bytes0(),
@@ -45,7 +45,7 @@
 )
 
 transaction2 = Transaction(
-    U256(1),
+    U64(1),
     Uint(2),
     Uint(3),
     Bytes0(),
diff --git a/tests/tangerine_whistle/test_rlp.py b/tests/tangerine_whistle/test_rlp.py
index 1d0414f7d9..7d05dd7946 100644
--- a/tests/tangerine_whistle/test_rlp.py
+++ b/tests/tangerine_whistle/test_rlp.py
@@ -1,7 +1,7 @@
 import pytest
 
 import ethereum.rlp as rlp
-from ethereum.base_types import U256, Bytes, Bytes0, Bytes8, Uint
+from ethereum.base_types import U64, U256, Bytes, Bytes0, Bytes8, Uint
 from ethereum.crypto.hash import keccak256
 from ethereum.tangerine_whistle.blocks import Block, Header, Log, Receipt
 from ethereum.tangerine_whistle.transactions import Transaction
@@ -33,7 +33,7 @@
 )
 
 transaction1 = Transaction(
-    U256(1),
+    U64(1),
     Uint(2),
     Uint(3),
     Bytes0(),
@@ -45,7 +45,7 @@
 )
 
 transaction2 = Transaction(
-    U256(1),
+    U64(1),
     Uint(2),
     Uint(3),
     Bytes0(),