diff --git a/rddlrepository/core/info.py b/rddlrepository/core/info.py
index e8918c4..f823548 100644
--- a/rddlrepository/core/info.py
+++ b/rddlrepository/core/info.py
@@ -1,7 +1,7 @@
 import os.path
 import sys
 import importlib.util
-from typing import Dict, List
+from typing import Any, Dict, List
 
 from .error import (
     RDDLRepoInstanceNotExistError,
@@ -17,7 +17,7 @@
 
 class ProblemInfo:
 
-    def __init__(self, problem_data: Dict) -> None:
+    def __init__(self, problem_data: Dict[str, Any]) -> None:
         self.name = problem_data['name']
         self.desc = problem_data['description']
         self.loc = problem_data['location']
diff --git a/rddlrepository/core/manager.py b/rddlrepository/core/manager.py
index d4ceb00..5aca72b 100644
--- a/rddlrepository/core/manager.py
+++ b/rddlrepository/core/manager.py
@@ -3,7 +3,7 @@
 import os
 import importlib
 import csv
-from typing import Dict, List
+from typing import Dict, List, Optional
 
 from .error import (
     RDDLRepoDomainNotExistError,
@@ -25,7 +25,7 @@
 
 class RDDLRepoManager:
 
-    def __init__(self, rebuild=False) -> None:
+    def __init__(self, rebuild: bool=False) -> None:
         self.archiver_dict = {}
         self.archive_by_context = {}
         
@@ -217,7 +217,7 @@ def register_context(self, context: str, refresh: bool=True) -> None:
         print(f'Context <{context}> was successfully registered in rddlrepository.')
     
     def register_domain(self, name: str, context: str, rddl: str,
-                        desc: str=None, viz: str='', refresh: bool=True) -> None:
+                        desc: Optional[str]=None, viz: str='', refresh: bool=True) -> None:
         domains = self.list_problems_by_context(context)
         if name in domains:
             raise RDDLRepoProblemDuplicationError(