diff --git a/application/prompt_client/prompt_client.py b/application/prompt_client/prompt_client.py
index 355dcbb2e..f5a912ab2 100644
--- a/application/prompt_client/prompt_client.py
+++ b/application/prompt_client/prompt_client.py
@@ -20,7 +20,7 @@
 logger = logging.getLogger(__name__)
 logger.setLevel(logging.INFO)
 
-SIMILARITY_THRESHOLD = os.environ.get("CHATBOT_SIMILARITY_THRESHOLD", None) or 0.7
+SIMILARITY_THRESHOLD = float(os.environ.get("CHATBOT_SIMILARITY_THRESHOLD", "0.7"))
 
 
 def is_valid_url(url):