diff --git a/async_substrate_interface/types.py b/async_substrate_interface/types.py
index 52cf69b..f1b4917 100644
--- a/async_substrate_interface/types.py
+++ b/async_substrate_interface/types.py
@@ -6,7 +6,9 @@
 from datetime import datetime
 from typing import Optional, Union, Any
 
+import scalecodec.types
 from bt_decode import PortableRegistry, encode as encode_by_type_string
+from bt_decode.bt_decode import MetadataV15
 from scalecodec import ss58_encode, ss58_decode, is_valid_ss58_address
 from scalecodec.base import RuntimeConfigurationObject, ScaleBytes
 from scalecodec.type_registry import load_type_registry_preset
@@ -121,13 +123,13 @@ class Runtime:
     def __init__(
         self,
         chain: str,
-        metadata,
-        type_registry,
+        metadata: scalecodec.types.GenericMetadataVersioned,
+        type_registry: dict,
         runtime_config: Optional[RuntimeConfigurationObject] = None,
-        metadata_v15=None,
-        runtime_info=None,
-        registry=None,
-        ss58_format=SS58_FORMAT,
+        metadata_v15: Optional[MetadataV15] = None,
+        runtime_info: Optional[dict] = None,
+        registry: Optional[PortableRegistry] = None,
+        ss58_format: int = SS58_FORMAT,
     ):
         self.ss58_format = ss58_format
         self.config = {}