diff --git a/compose/config/config.py b/compose/config/config.py
index 3ecdd29d7b..56e6e796ba 100644
--- a/compose/config/config.py
+++ b/compose/config/config.py
@@ -104,6 +104,8 @@ def find(base_dir, filenames):
         filenames = [os.path.join(base_dir, f) for f in filenames]
     else:
         filenames = get_default_config_files(base_dir)
+
+    log.debug("Using configuration files: {}".format(",".join(filenames)))
     return ConfigDetails(
         os.path.dirname(filenames[0]),
         [ConfigFile(f, load_yaml(f)) for f in filenames])