diff --git a/requirements-dev.txt b/requirements-dev.txt
index 4b083b9c8..405265ef2 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -3,7 +3,7 @@ flake8
 isort==5.13.2
 nbsphinx
 pre-commit
-pyright==1.1.366
+pyright==1.1.378
 pytest
 pytest-asyncio
 pytest-cov
diff --git a/src/poke_env/environment/observation.py b/src/poke_env/environment/observation.py
index ac8b05a83..1fcf8eca4 100644
--- a/src/poke_env/environment/observation.py
+++ b/src/poke_env/environment/observation.py
@@ -22,10 +22,8 @@ class Observation:
     weather: Dict[Weather, int] = field(default_factory=dict)
     fields: Dict[Field, int] = field(default_factory=dict)
 
-    active_pokemon: Union[ObservedPokemon, List[Optional[ObservedPokemon]], None] = None
-    opponent_active_pokemon: Union[
-        ObservedPokemon, List[Optional[ObservedPokemon]], None
-    ] = None
+    active_pokemon: Union[ObservedPokemon, None, List[ObservedPokemon]] = None
+    opponent_active_pokemon: Union[ObservedPokemon, List[ObservedPokemon], None] = None
 
     # The player's team, so we can track states of mons throughout the battle
     team: Dict[str, Optional[ObservedPokemon]] = field(default_factory=dict)