diff --git a/transactron/core.py b/transactron/core.py
index c4c34f8cc..e9ab302da 100644
--- a/transactron/core.py
+++ b/transactron/core.py
@@ -2,7 +2,18 @@
 from collections.abc import Sequence, Iterable, Callable, Mapping, Iterator
 from contextlib import contextmanager
 from enum import Enum, auto
-from typing import ClassVar, NoReturn, TypeAlias, TypedDict, Union, Optional, Tuple
+from typing import (
+    ClassVar,
+    NoReturn,
+    TypeAlias,
+    TypedDict,
+    Union,
+    Optional,
+    Tuple,
+    TypeVar,
+    Protocol,
+    runtime_checkable,
+)
 from graphlib import TopologicalSorter
 from typing_extensions import Self
 from amaranth import *
@@ -38,6 +49,7 @@
 TransactionScheduler: TypeAlias = Callable[["MethodMap", TransactionGraph, TransactionGraphCC, PriorityOrder], Module]
 RecordDict: TypeAlias = ValueLike | Mapping[str, "RecordDict"]
 TransactionOrMethod: TypeAlias = Union["Transaction", "Method"]
+TransactionOrMethodBound = TypeVar("TransactionOrMethodBound", bound=Union["Transaction", "Method"])
 
 
 class Priority(Enum):
@@ -670,15 +682,20 @@ def elaborate(self, platform):
         return self.main_module
 
 
-class TransactionBase(Owned):
+@runtime_checkable
+class TransactionBase(Owned, Protocol):
     stack: ClassVar[list[Union["Transaction", "Method"]]] = []
     def_counter: ClassVar[count] = count()
     def_order: int
     defined: bool = False
     name: str
+    method_uses: dict["Method", Tuple[ValueLike, ValueLike]]
+    relations: list[RelationBase]
+    simultaneous_list: list[TransactionOrMethod]
+    independent_list: list[TransactionOrMethod]
 
     def __init__(self):
-        self.method_uses: dict[Method, Tuple[ValueLike, ValueLike]] = dict()
+        self.method_uses: dict["Method", Tuple[ValueLike, ValueLike]] = dict()
         self.relations: list[RelationBase] = []
         self.simultaneous_list: list[TransactionOrMethod] = []
         self.independent_list: list[TransactionOrMethod] = []
@@ -769,9 +786,7 @@ def _independent(self, *others: TransactionOrMethod) -> None:
         self.independent_list += others
 
     @contextmanager
-    def context(self, m: TModule) -> Iterator[Self]:
-        assert isinstance(self, Transaction) or isinstance(self, Method)  # for typing
-
+    def context(self: TransactionOrMethodBound, m: TModule) -> Iterator[TransactionOrMethodBound]:
         parent = TransactionBase.peek()
         if parent is not None:
             parent.schedule_before(self)
diff --git a/transactron/graph.py b/transactron/graph.py
index 2deaf24a0..4cd51d067 100644
--- a/transactron/graph.py
+++ b/transactron/graph.py
@@ -3,15 +3,14 @@
 """
 
 from enum import IntFlag
-from abc import ABC
 from collections import defaultdict
-from typing import Literal, Optional
+from typing import Literal, Optional, Protocol
 
 from amaranth.hdl.ir import Elaboratable, Fragment
 from .tracing import TracingFragment
 
 
-class Owned(ABC):
+class Owned(Protocol):
     name: str
     owner: Optional[Elaboratable]