diff --git a/homeassistant/helpers/translation.py b/homeassistant/helpers/translation.py
index 79ac3a0c5b7..41ad591d878 100644
--- a/homeassistant/helpers/translation.py
+++ b/homeassistant/helpers/translation.py
@@ -190,6 +190,8 @@ async def _async_get_component_strings(
 class _TranslationCache:
     """Cache for flattened translations."""
 
+    __slots__ = ("hass", "loaded", "cache")
+
     def __init__(self, hass: HomeAssistant) -> None:
         """Initialize the cache."""
         self.hass = hass