diff --git a/eppo_client/client.py b/eppo_client/client.py
index 6fd5606..551d849 100644
--- a/eppo_client/client.py
+++ b/eppo_client/client.py
@@ -469,7 +469,7 @@ def convert_context_attributes_to_attributes(
         return subject_context
 
     # ignoring type because Dict[str, str] satisfies Dict[str, str | ...] but mypy does not understand
-    return subject_context.numeric_attributes | subject_context.categorical_attributes  # type: ignore
+    return {**subject_context.numeric_attributes, **subject_context.categorical_attributes}  # type: ignore
 
 
 def convert_attributes_to_context_attributes(
diff --git a/eppo_client/version.py b/eppo_client/version.py
index 7198df6..5b94c7d 100644
--- a/eppo_client/version.py
+++ b/eppo_client/version.py
@@ -1,4 +1,4 @@
 # Note to developers: When ready to bump to 4.0, please change
 # the `POLL_INTERVAL_SECONDS` constant in `eppo_client/constants.py`
 # to 30 seconds to match the behavior of the other server SDKs.
-__version__ = "3.5.2"
+__version__ = "3.5.3"