diff --git a/pydantic_ai_slim/pydantic_ai/_agent_graph.py b/pydantic_ai_slim/pydantic_ai/_agent_graph.py
index 2f27aac8da..e3785e7adf 100644
--- a/pydantic_ai_slim/pydantic_ai/_agent_graph.py
+++ b/pydantic_ai_slim/pydantic_ai/_agent_graph.py
@@ -371,9 +371,8 @@ async def run(
     ) -> Union[ModelRequestNode[DepsT, NodeRunEndT], End[result.FinalResult[NodeRunEndT]]]:  # noqa UP007
         async with self.stream(ctx):
             pass
-
-        assert (next_node := self._next_node) is not None, 'the stream should set `self._next_node` before it ends'
-        return next_node
+        assert self._next_node is not None, 'the stream should set `self._next_node` before it ends'
+        return self._next_node
 
     @asynccontextmanager
     async def stream(
diff --git a/pydantic_ai_slim/pydantic_ai/agent.py b/pydantic_ai_slim/pydantic_ai/agent.py
index 4d4eeac2fa..a532fe4659 100644
--- a/pydantic_ai_slim/pydantic_ai/agent.py
+++ b/pydantic_ai_slim/pydantic_ai/agent.py
@@ -329,8 +329,8 @@ async def main():
             async for _ in agent_run:
                 pass
 
-        assert (final_result := agent_run.result) is not None, 'The graph run did not finish properly'
-        return final_result
+        assert agent_run.result is not None, 'The graph run did not finish properly'
+        return agent_run.result
 
     @asynccontextmanager
     async def iter(
diff --git a/pyproject.toml b/pyproject.toml
index adcd5dfece..5f7a48fafc 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -102,7 +102,16 @@ include = [
 ]
 
 [tool.ruff.lint]
-extend-select = ["Q", "RUF100", "C90", "UP", "I", "D", "TID251"]
+extend-select = [
+    "Q",
+    "RUF100",
+    "RUF018",  # https://docs.astral.sh/ruff/rules/assignment-in-assert/
+    "C90",
+    "UP",
+    "I",
+    "D",
+    "TID251",
+]
 flake8-quotes = { inline-quotes = "single", multiline-quotes = "double" }
 isort = { combine-as-imports = true, known-first-party = ["pydantic_ai"] }
 mccabe = { max-complexity = 15 }