diff --git a/foodie_engagement_tweet.py b/foodie_engagement_tweet.py
index 8b6b7df..04ef41f 100644
--- a/foodie_engagement_tweet.py
+++ b/foodie_engagement_tweet.py
@@ -133,11 +133,13 @@ try:
         if "username" not in bg:
             logging.error(f"Invalid entry in {AUTHOR_BACKGROUNDS_FILE}: Missing 'username' key in {bg}")
             raise ValueError("Each author background must have a 'username' key")
+        if "engagement_themes" not in bg or not isinstance(bg["engagement_themes"], list) or not bg["engagement_themes"]:
+            logging.error(f"Invalid entry in {AUTHOR_BACKGROUNDS_FILE}: Missing or invalid 'engagement_themes' for {bg.get('username', 'unknown')}: {bg}")
+            raise ValueError("Each author background must have a non-empty 'engagement_themes' list")
         username = bg["username"]
         if not isinstance(username, str):
             logging.error(f"Invalid username type in {AUTHOR_BACKGROUNDS_FILE}: {username} (type: {type(username)})")
             raise ValueError("Username must be a string")
-        # Normalize the username to handle encoding differences
         cleaned_username = unicodedata.normalize('NFC', username.strip().lower())
         AUTHOR_BACKGROUNDS[cleaned_username] = bg
         logging.debug(f"Added to AUTHOR_BACKGROUNDS: key='{cleaned_username}', value={bg}")