diff --git a/src/ethereum/arrow_glacier/trie.py b/src/ethereum/arrow_glacier/trie.py
index 069b8127e2..4353ab8963 100644
--- a/src/ethereum/arrow_glacier/trie.py
+++ b/src/ethereum/arrow_glacier/trie.py
@@ -24,6 +24,7 @@
     MutableMapping,
     Optional,
     Sequence,
+    Tuple,
     TypeVar,
     Union,
 )
@@ -97,7 +98,7 @@ class ExtensionNode:
 class BranchNode:
     """Branch node in the Merkle Trie"""
 
-    subnodes: List[rlp.Extended]
+    subnodes: Tuple[rlp.Extended, ...]
     value: rlp.Extended
 
 
@@ -137,7 +138,7 @@ def encode_internal_node(node: Optional[InternalNode]) -> rlp.Extended:
             node.subnode,
         )
     elif isinstance(node, BranchNode):
-        unencoded = node.subnodes + [node.value]
+        unencoded = list(node.subnodes) + [node.value]
     else:
         raise AssertionError(f"Invalid internal node type {type(node)}!")
 
@@ -459,9 +460,9 @@ def patricialize(
             branches[key[level]][key] = obj[key]
 
     return BranchNode(
-        [
+        (
             encode_internal_node(patricialize(branches[k], level + Uint(1)))
             for k in range(16)
-        ],
+        ),
         value,
     )
diff --git a/src/ethereum/berlin/trie.py b/src/ethereum/berlin/trie.py
index 5ab348f521..e42d136aef 100644
--- a/src/ethereum/berlin/trie.py
+++ b/src/ethereum/berlin/trie.py
@@ -24,6 +24,7 @@
     MutableMapping,
     Optional,
     Sequence,
+    Tuple,
     TypeVar,
     Union,
 )
@@ -97,7 +98,7 @@ class ExtensionNode:
 class BranchNode:
     """Branch node in the Merkle Trie"""
 
-    subnodes: List[rlp.Extended]
+    subnodes: Tuple[rlp.Extended, ...]
     value: rlp.Extended
 
 
@@ -137,7 +138,7 @@ def encode_internal_node(node: Optional[InternalNode]) -> rlp.Extended:
             node.subnode,
         )
     elif isinstance(node, BranchNode):
-        unencoded = node.subnodes + [node.value]
+        unencoded = list(node.subnodes) + [node.value]
     else:
         raise AssertionError(f"Invalid internal node type {type(node)}!")
 
@@ -459,9 +460,9 @@ def patricialize(
             branches[key[level]][key] = obj[key]
 
     return BranchNode(
-        [
+        (
             encode_internal_node(patricialize(branches[k], level + Uint(1)))
             for k in range(16)
-        ],
+        ),
         value,
     )
diff --git a/src/ethereum/byzantium/trie.py b/src/ethereum/byzantium/trie.py
index 9d2a8f256e..10377dfddd 100644
--- a/src/ethereum/byzantium/trie.py
+++ b/src/ethereum/byzantium/trie.py
@@ -24,6 +24,7 @@
     MutableMapping,
     Optional,
     Sequence,
+    Tuple,
     TypeVar,
     Union,
 )
@@ -97,7 +98,7 @@ class ExtensionNode:
 class BranchNode:
     """Branch node in the Merkle Trie"""
 
-    subnodes: List[rlp.Extended]
+    subnodes: Tuple[rlp.Extended, ...]
     value: rlp.Extended
 
 
@@ -137,7 +138,7 @@ def encode_internal_node(node: Optional[InternalNode]) -> rlp.Extended:
             node.subnode,
         )
     elif isinstance(node, BranchNode):
-        unencoded = node.subnodes + [node.value]
+        unencoded = list(node.subnodes) + [node.value]
     else:
         raise AssertionError(f"Invalid internal node type {type(node)}!")
 
@@ -459,9 +460,9 @@ def patricialize(
             branches[key[level]][key] = obj[key]
 
     return BranchNode(
-        [
+        (
             encode_internal_node(patricialize(branches[k], level + Uint(1)))
             for k in range(16)
-        ],
+        ),
         value,
     )
diff --git a/src/ethereum/cancun/trie.py b/src/ethereum/cancun/trie.py
index db0394cdb2..268050ca1a 100644
--- a/src/ethereum/cancun/trie.py
+++ b/src/ethereum/cancun/trie.py
@@ -24,6 +24,7 @@
     MutableMapping,
     Optional,
     Sequence,
+    Tuple,
     TypeVar,
     Union,
 )
@@ -100,7 +101,7 @@ class ExtensionNode:
 class BranchNode:
     """Branch node in the Merkle Trie"""
 
-    subnodes: List[rlp.Extended]
+    subnodes: Tuple[rlp.Extended, ...]
     value: rlp.Extended
 
 
@@ -140,7 +141,7 @@ def encode_internal_node(node: Optional[InternalNode]) -> rlp.Extended:
             node.subnode,
         )
     elif isinstance(node, BranchNode):
-        unencoded = node.subnodes + [node.value]
+        unencoded = list(node.subnodes) + [node.value]
     else:
         raise AssertionError(f"Invalid internal node type {type(node)}!")
 
@@ -462,9 +463,9 @@ def patricialize(
             branches[key[level]][key] = obj[key]
 
     return BranchNode(
-        [
+        (
             encode_internal_node(patricialize(branches[k], level + Uint(1)))
             for k in range(16)
-        ],
+        ),
         value,
     )
diff --git a/src/ethereum/constantinople/trie.py b/src/ethereum/constantinople/trie.py
index 6d61f3aaa9..3687231873 100644
--- a/src/ethereum/constantinople/trie.py
+++ b/src/ethereum/constantinople/trie.py
@@ -24,6 +24,7 @@
     MutableMapping,
     Optional,
     Sequence,
+    Tuple,
     TypeVar,
     Union,
 )
@@ -97,7 +98,7 @@ class ExtensionNode:
 class BranchNode:
     """Branch node in the Merkle Trie"""
 
-    subnodes: List[rlp.Extended]
+    subnodes: Tuple[rlp.Extended, ...]
     value: rlp.Extended
 
 
@@ -137,7 +138,7 @@ def encode_internal_node(node: Optional[InternalNode]) -> rlp.Extended:
             node.subnode,
         )
     elif isinstance(node, BranchNode):
-        unencoded = node.subnodes + [node.value]
+        unencoded = list(node.subnodes) + [node.value]
     else:
         raise AssertionError(f"Invalid internal node type {type(node)}!")
 
@@ -459,9 +460,9 @@ def patricialize(
             branches[key[level]][key] = obj[key]
 
     return BranchNode(
-        [
+        (
             encode_internal_node(patricialize(branches[k], level + Uint(1)))
             for k in range(16)
-        ],
+        ),
         value,
     )
diff --git a/src/ethereum/dao_fork/trie.py b/src/ethereum/dao_fork/trie.py
index 0b1bd95d96..40b70ad9e3 100644
--- a/src/ethereum/dao_fork/trie.py
+++ b/src/ethereum/dao_fork/trie.py
@@ -24,6 +24,7 @@
     MutableMapping,
     Optional,
     Sequence,
+    Tuple,
     TypeVar,
     Union,
 )
@@ -97,7 +98,7 @@ class ExtensionNode:
 class BranchNode:
     """Branch node in the Merkle Trie"""
 
-    subnodes: List[rlp.Extended]
+    subnodes: Tuple[rlp.Extended, ...]
     value: rlp.Extended
 
 
@@ -137,7 +138,7 @@ def encode_internal_node(node: Optional[InternalNode]) -> rlp.Extended:
             node.subnode,
         )
     elif isinstance(node, BranchNode):
-        unencoded = node.subnodes + [node.value]
+        unencoded = list(node.subnodes) + [node.value]
     else:
         raise AssertionError(f"Invalid internal node type {type(node)}!")
 
@@ -459,9 +460,9 @@ def patricialize(
             branches[key[level]][key] = obj[key]
 
     return BranchNode(
-        [
+        (
             encode_internal_node(patricialize(branches[k], level + Uint(1)))
             for k in range(16)
-        ],
+        ),
         value,
     )
diff --git a/src/ethereum/frontier/trie.py b/src/ethereum/frontier/trie.py
index 587e811172..d4cd75ab4c 100644
--- a/src/ethereum/frontier/trie.py
+++ b/src/ethereum/frontier/trie.py
@@ -24,6 +24,7 @@
     MutableMapping,
     Optional,
     Sequence,
+    Tuple,
     TypeVar,
     Union,
 )
@@ -96,7 +97,7 @@ class ExtensionNode:
 class BranchNode:
     """Branch node in the Merkle Trie"""
 
-    subnodes: List[rlp.Extended]
+    subnodes: Tuple[rlp.Extended, ...]
     value: rlp.Extended
 
 
@@ -136,7 +137,7 @@ def encode_internal_node(node: Optional[InternalNode]) -> rlp.Extended:
             node.subnode,
         )
     elif isinstance(node, BranchNode):
-        unencoded = node.subnodes + [node.value]
+        unencoded = list(node.subnodes) + [node.value]
     else:
         raise AssertionError(f"Invalid internal node type {type(node)}!")
 
@@ -460,9 +461,9 @@ def patricialize(
             branches[key[level]][key] = obj[key]
 
     return BranchNode(
-        [
+        (
             encode_internal_node(patricialize(branches[k], level + Uint(1)))
             for k in range(16)
-        ],
+        ),
         value,
     )
diff --git a/src/ethereum/gray_glacier/trie.py b/src/ethereum/gray_glacier/trie.py
index e6ee3e9bef..84f0beaabf 100644
--- a/src/ethereum/gray_glacier/trie.py
+++ b/src/ethereum/gray_glacier/trie.py
@@ -24,6 +24,7 @@
     MutableMapping,
     Optional,
     Sequence,
+    Tuple,
     TypeVar,
     Union,
 )
@@ -97,7 +98,7 @@ class ExtensionNode:
 class BranchNode:
     """Branch node in the Merkle Trie"""
 
-    subnodes: List[rlp.Extended]
+    subnodes: Tuple[rlp.Extended, ...]
     value: rlp.Extended
 
 
@@ -137,7 +138,7 @@ def encode_internal_node(node: Optional[InternalNode]) -> rlp.Extended:
             node.subnode,
         )
     elif isinstance(node, BranchNode):
-        unencoded = node.subnodes + [node.value]
+        unencoded = list(node.subnodes) + [node.value]
     else:
         raise AssertionError(f"Invalid internal node type {type(node)}!")
 
@@ -459,9 +460,9 @@ def patricialize(
             branches[key[level]][key] = obj[key]
 
     return BranchNode(
-        [
+        (
             encode_internal_node(patricialize(branches[k], level + Uint(1)))
             for k in range(16)
-        ],
+        ),
         value,
     )
diff --git a/src/ethereum/homestead/trie.py b/src/ethereum/homestead/trie.py
index 5294a2ba0d..2bdf78b9be 100644
--- a/src/ethereum/homestead/trie.py
+++ b/src/ethereum/homestead/trie.py
@@ -24,6 +24,7 @@
     MutableMapping,
     Optional,
     Sequence,
+    Tuple,
     TypeVar,
     Union,
 )
@@ -97,7 +98,7 @@ class ExtensionNode:
 class BranchNode:
     """Branch node in the Merkle Trie"""
 
-    subnodes: List[rlp.Extended]
+    subnodes: Tuple[rlp.Extended, ...]
     value: rlp.Extended
 
 
@@ -137,7 +138,7 @@ def encode_internal_node(node: Optional[InternalNode]) -> rlp.Extended:
             node.subnode,
         )
     elif isinstance(node, BranchNode):
-        unencoded = node.subnodes + [node.value]
+        unencoded = list(node.subnodes) + [node.value]
     else:
         raise AssertionError(f"Invalid internal node type {type(node)}!")
 
@@ -459,9 +460,9 @@ def patricialize(
             branches[key[level]][key] = obj[key]
 
     return BranchNode(
-        [
+        (
             encode_internal_node(patricialize(branches[k], level + Uint(1)))
             for k in range(16)
-        ],
+        ),
         value,
     )
diff --git a/src/ethereum/istanbul/trie.py b/src/ethereum/istanbul/trie.py
index a1a4cfbf98..347ffb0bd0 100644
--- a/src/ethereum/istanbul/trie.py
+++ b/src/ethereum/istanbul/trie.py
@@ -24,6 +24,7 @@
     MutableMapping,
     Optional,
     Sequence,
+    Tuple,
     TypeVar,
     Union,
 )
@@ -97,7 +98,7 @@ class ExtensionNode:
 class BranchNode:
     """Branch node in the Merkle Trie"""
 
-    subnodes: List[rlp.Extended]
+    subnodes: Tuple[rlp.Extended, ...]
     value: rlp.Extended
 
 
@@ -137,7 +138,7 @@ def encode_internal_node(node: Optional[InternalNode]) -> rlp.Extended:
             node.subnode,
         )
     elif isinstance(node, BranchNode):
-        unencoded = node.subnodes + [node.value]
+        unencoded = list(node.subnodes) + [node.value]
     else:
         raise AssertionError(f"Invalid internal node type {type(node)}!")
 
@@ -459,9 +460,9 @@ def patricialize(
             branches[key[level]][key] = obj[key]
 
     return BranchNode(
-        [
+        (
             encode_internal_node(patricialize(branches[k], level + Uint(1)))
             for k in range(16)
-        ],
+        ),
         value,
     )
diff --git a/src/ethereum/london/trie.py b/src/ethereum/london/trie.py
index 03e230531c..b84ed19f71 100644
--- a/src/ethereum/london/trie.py
+++ b/src/ethereum/london/trie.py
@@ -24,6 +24,7 @@
     MutableMapping,
     Optional,
     Sequence,
+    Tuple,
     TypeVar,
     Union,
 )
@@ -97,7 +98,7 @@ class ExtensionNode:
 class BranchNode:
     """Branch node in the Merkle Trie"""
 
-    subnodes: List[rlp.Extended]
+    subnodes: Tuple[rlp.Extended, ...]
     value: rlp.Extended
 
 
@@ -137,7 +138,7 @@ def encode_internal_node(node: Optional[InternalNode]) -> rlp.Extended:
             node.subnode,
         )
     elif isinstance(node, BranchNode):
-        unencoded = node.subnodes + [node.value]
+        unencoded = list(node.subnodes) + [node.value]
     else:
         raise AssertionError(f"Invalid internal node type {type(node)}!")
 
@@ -459,9 +460,9 @@ def patricialize(
             branches[key[level]][key] = obj[key]
 
     return BranchNode(
-        [
+        (
             encode_internal_node(patricialize(branches[k], level + Uint(1)))
             for k in range(16)
-        ],
+        ),
         value,
     )
diff --git a/src/ethereum/muir_glacier/trie.py b/src/ethereum/muir_glacier/trie.py
index f2e4f29460..be99b895ce 100644
--- a/src/ethereum/muir_glacier/trie.py
+++ b/src/ethereum/muir_glacier/trie.py
@@ -24,6 +24,7 @@
     MutableMapping,
     Optional,
     Sequence,
+    Tuple,
     TypeVar,
     Union,
 )
@@ -97,7 +98,7 @@ class ExtensionNode:
 class BranchNode:
     """Branch node in the Merkle Trie"""
 
-    subnodes: List[rlp.Extended]
+    subnodes: Tuple[rlp.Extended, ...]
     value: rlp.Extended
 
 
@@ -137,7 +138,7 @@ def encode_internal_node(node: Optional[InternalNode]) -> rlp.Extended:
             node.subnode,
         )
     elif isinstance(node, BranchNode):
-        unencoded = node.subnodes + [node.value]
+        unencoded = list(node.subnodes) + [node.value]
     else:
         raise AssertionError(f"Invalid internal node type {type(node)}!")
 
@@ -459,9 +460,9 @@ def patricialize(
             branches[key[level]][key] = obj[key]
 
     return BranchNode(
-        [
+        (
             encode_internal_node(patricialize(branches[k], level + Uint(1)))
             for k in range(16)
-        ],
+        ),
         value,
     )
diff --git a/src/ethereum/paris/trie.py b/src/ethereum/paris/trie.py
index ccd99a17af..cd23509958 100644
--- a/src/ethereum/paris/trie.py
+++ b/src/ethereum/paris/trie.py
@@ -24,6 +24,7 @@
     MutableMapping,
     Optional,
     Sequence,
+    Tuple,
     TypeVar,
     Union,
 )
@@ -97,7 +98,7 @@ class ExtensionNode:
 class BranchNode:
     """Branch node in the Merkle Trie"""
 
-    subnodes: List[rlp.Extended]
+    subnodes: Tuple[rlp.Extended, ...]
     value: rlp.Extended
 
 
@@ -137,7 +138,7 @@ def encode_internal_node(node: Optional[InternalNode]) -> rlp.Extended:
             node.subnode,
         )
     elif isinstance(node, BranchNode):
-        unencoded = node.subnodes + [node.value]
+        unencoded = list(node.subnodes) + [node.value]
     else:
         raise AssertionError(f"Invalid internal node type {type(node)}!")
 
@@ -459,9 +460,9 @@ def patricialize(
             branches[key[level]][key] = obj[key]
 
     return BranchNode(
-        [
+        (
             encode_internal_node(patricialize(branches[k], level + Uint(1)))
             for k in range(16)
-        ],
+        ),
         value,
     )
diff --git a/src/ethereum/shanghai/trie.py b/src/ethereum/shanghai/trie.py
index 020e9900c4..7ce098e547 100644
--- a/src/ethereum/shanghai/trie.py
+++ b/src/ethereum/shanghai/trie.py
@@ -24,6 +24,7 @@
     MutableMapping,
     Optional,
     Sequence,
+    Tuple,
     TypeVar,
     Union,
 )
@@ -100,7 +101,7 @@ class ExtensionNode:
 class BranchNode:
     """Branch node in the Merkle Trie"""
 
-    subnodes: List[rlp.Extended]
+    subnodes: Tuple[rlp.Extended, ...]
     value: rlp.Extended
 
 
@@ -140,7 +141,7 @@ def encode_internal_node(node: Optional[InternalNode]) -> rlp.Extended:
             node.subnode,
         )
     elif isinstance(node, BranchNode):
-        unencoded = node.subnodes + [node.value]
+        unencoded = list(node.subnodes) + [node.value]
     else:
         raise AssertionError(f"Invalid internal node type {type(node)}!")
 
@@ -462,9 +463,9 @@ def patricialize(
             branches[key[level]][key] = obj[key]
 
     return BranchNode(
-        [
+        (
             encode_internal_node(patricialize(branches[k], level + Uint(1)))
             for k in range(16)
-        ],
+        ),
         value,
     )
diff --git a/src/ethereum/spurious_dragon/trie.py b/src/ethereum/spurious_dragon/trie.py
index 1b13975d22..3e7f78a498 100644
--- a/src/ethereum/spurious_dragon/trie.py
+++ b/src/ethereum/spurious_dragon/trie.py
@@ -24,6 +24,7 @@
     MutableMapping,
     Optional,
     Sequence,
+    Tuple,
     TypeVar,
     Union,
 )
@@ -97,7 +98,7 @@ class ExtensionNode:
 class BranchNode:
     """Branch node in the Merkle Trie"""
 
-    subnodes: List[rlp.Extended]
+    subnodes: Tuple[rlp.Extended, ...]
     value: rlp.Extended
 
 
@@ -137,7 +138,7 @@ def encode_internal_node(node: Optional[InternalNode]) -> rlp.Extended:
             node.subnode,
         )
     elif isinstance(node, BranchNode):
-        unencoded = node.subnodes + [node.value]
+        unencoded = list(node.subnodes) + [node.value]
     else:
         raise AssertionError(f"Invalid internal node type {type(node)}!")
 
@@ -459,9 +460,9 @@ def patricialize(
             branches[key[level]][key] = obj[key]
 
     return BranchNode(
-        [
+        (
             encode_internal_node(patricialize(branches[k], level + Uint(1)))
             for k in range(16)
-        ],
+        ),
         value,
     )
diff --git a/src/ethereum/tangerine_whistle/trie.py b/src/ethereum/tangerine_whistle/trie.py
index 884faff508..f75172df62 100644
--- a/src/ethereum/tangerine_whistle/trie.py
+++ b/src/ethereum/tangerine_whistle/trie.py
@@ -24,6 +24,7 @@
     MutableMapping,
     Optional,
     Sequence,
+    Tuple,
     TypeVar,
     Union,
 )
@@ -97,7 +98,7 @@ class ExtensionNode:
 class BranchNode:
     """Branch node in the Merkle Trie"""
 
-    subnodes: List[rlp.Extended]
+    subnodes: Tuple[rlp.Extended, ...]
     value: rlp.Extended
 
 
@@ -137,7 +138,7 @@ def encode_internal_node(node: Optional[InternalNode]) -> rlp.Extended:
             node.subnode,
         )
     elif isinstance(node, BranchNode):
-        unencoded = node.subnodes + [node.value]
+        unencoded = list(node.subnodes) + [node.value]
     else:
         raise AssertionError(f"Invalid internal node type {type(node)}!")
 
@@ -459,9 +460,9 @@ def patricialize(
             branches[key[level]][key] = obj[key]
 
     return BranchNode(
-        [
+        (
             encode_internal_node(patricialize(branches[k], level + Uint(1)))
             for k in range(16)
-        ],
+        ),
         value,
     )