diff --git a/alchemiscale/interface/client.py b/alchemiscale/interface/client.py
index be9414b2..eaba27b7 100644
--- a/alchemiscale/interface/client.py
+++ b/alchemiscale/interface/client.py
@@ -88,7 +88,7 @@ def get_scoped_key(self, obj: GufeTokenizable, scope: Scope) -> ScopedKey:
                 "Scope for a ScopedKey must be specific; it cannot contain wildcards."
             )
 
-    def check_exists(self, scoped_key: Union[ScopedKey, str]) -> bool:
+    def check_exists(self, scoped_key: ScopedKey | str) -> bool:
         """Returns ``True`` if the given ScopedKey represents an object in the database."""
         return self._get_resource(f"/exists/{scoped_key}")