diff --git a/frida/core.py b/frida/core.py
index 779308c..b6dc5c8 100644
--- a/frida/core.py
+++ b/frida/core.py
@@ -401,7 +401,7 @@ def on_cancelled() -> None:
 
         return result.value
 
-    def _on_rpc_message(self, request_id: int, operation: str, params, data) -> None:
+    def _on_rpc_message(self, request_id: int, operation: str, params: List[Any], data: Optional[bytes]) -> None:
         if operation in ("ok", "error"):
             callback = self._pending.pop(request_id, None)
             if callback is None:
diff --git a/pyproject.toml b/pyproject.toml
index 85966e1..9d6978b 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -8,3 +8,6 @@ line-length = 120
 [tool.isort]
 profile = "black"
 line_length = 120
+
+[tool.mypy]
+strict = true