diff --git a/pandas_datareader/_utils.py b/pandas_datareader/_utils.py
index 245cb33a..33338c1f 100644
--- a/pandas_datareader/_utils.py
+++ b/pandas_datareader/_utils.py
@@ -56,6 +56,7 @@ def _sanitize_dates(start, end):
 def _init_session(session):
     if session is None:
         session = requests.Session()
+        session.headers.update({'User-Agent': 'Firefox'})
         # do not set requests max_retries here to support arbitrary pause
     else:
         if not isinstance(session, requests.Session):