diff --git a/logging b/logging
index a3b99f1e..250359c4 100644
--- a/logging
+++ b/logging
@@ -53,7 +53,7 @@ formatter = full
 
 [formatter_simple]
 # Simple output format
-format = %(message)s
+format = [%(thread)x] %(levelname)s: %(message)s
 
 [formatter_full]
 # Full output format
diff --git a/radicale/log.py b/radicale/log.py
index 34d4e4cb..f550b489 100644
--- a/radicale/log.py
+++ b/radicale/log.py
@@ -56,7 +56,8 @@ def start(name="radicale", filename=None, debug=False):
                 "Logging configuration file '%s' not found, using stderr." %
                 filename)
         handler = logging.StreamHandler(sys.stderr)
-        handler.setFormatter(logging.Formatter("%(message)s"))
+        handler.setFormatter(
+            logging.Formatter("[%(thread)x] %(levelname)s: %(message)s"))
         logger.addHandler(handler)
     if debug:
         logger.setLevel(logging.DEBUG)