diff --git a/pydantic_ai_slim/pydantic_ai/models/__init__.py b/pydantic_ai_slim/pydantic_ai/models/__init__.py
index 79f603168..0da46941c 100644
--- a/pydantic_ai_slim/pydantic_ai/models/__init__.py
+++ b/pydantic_ai_slim/pydantic_ai/models/__init__.py
@@ -760,7 +760,7 @@ def _customize_tool_def(transformer: type[JsonSchemaTransformer], t: ToolDefinit
     schema_transformer = transformer(t.parameters_json_schema, strict=t.strict)
     parameters_json_schema = schema_transformer.walk()
     if t.strict is None:
-        t = replace(t, strict=schema_transformer.is_strict_compatible)
+        return replace(t, parameters_json_schema=parameters_json_schema, strict=schema_transformer.is_strict_compatible)
     return replace(t, parameters_json_schema=parameters_json_schema)