diff --git a/pygrocy/grocy_api_client.py b/pygrocy/grocy_api_client.py
index c8dc1cd..2b09b45 100644
--- a/pygrocy/grocy_api_client.py
+++ b/pygrocy/grocy_api_client.py
@@ -71,7 +71,7 @@ class RecipeDetailsResponse(BaseModel):
 class QuantityUnitData(BaseModel):
     id: int
     name: str
-    name_plural: str
+    name_plural: Optional[str] = None
     description: Optional[str] = None
     row_created_timestamp: datetime