diff --git a/src/models/requests.py b/src/models/requests.py
index 9f99c619..fcfaecca 100644
--- a/src/models/requests.py
+++ b/src/models/requests.py
@@ -366,7 +366,7 @@ def validate_categories(
         if len(value) == 0:
             return None  # Convert empty list to None for consistency
 
-        unique_categories = list(set(value))
+        unique_categories = list(dict.fromkeys(value))  # don't lose ordering
         return unique_categories
 
     @model_validator(mode="after")