diff --git a/op5_query_to_csv.py b/op5_query_to_csv.py
index b22847f..7920462 100644
--- a/op5_query_to_csv.py
+++ b/op5_query_to_csv.py
@@ -79,6 +79,10 @@
 # Process the response of the GET request.
 res = conn.getresponse()
 
+if res.status >= 400:
+    print('Server returned status code {status} - {reason}'.format(status=res.status, reason=res.reason))
+    exit(1)
+
 # Create JSON from the results.
 json_results = json.loads(res.read())