diff --git a/ennstatus/log.py b/ennstatus/log.py
--- a/ennstatus/log.py
+++ b/ennstatus/log.py
@@ -24,7 +24,7 @@ def init_logging(app):
     rotating_file_handler.setLevel(logging.INFO)
     rotating_file_handler.setFormatter(logging_formatter)
 
-    if app.debug or app.config['ENABLE_DEBUG_LOG']:
+    if app.debug or ('ENABLE_DEBUG_LOG' in app.config and app.config['ENABLE_DEBUG_LOG']):
         second_rotating_file_handler = logging.handlers.RotatingFileHandler(
             'log/ennstatus_debug.log',
             maxBytes=1300000,