diff --git a/beets/ui/__init__.py b/beets/ui/__init__.py
index 29e228497..75bce9e7a 100644
--- a/beets/ui/__init__.py
+++ b/beets/ui/__init__.py
@@ -1122,9 +1122,11 @@ def _configure(options):
     # special handling lets specified plugins get loaded before we
     # finish parsing the command line.
     if getattr(options, 'config', None) is not None:
-        config_path = options.config
+        overlay_path = options.config
         del options.config
-        config.set_file(config_path)
+        config.set_file(overlay_path)
+    else:
+        overlay_path = None
     config.set_args(options)
 
     # Configure the logger.
@@ -1133,6 +1135,10 @@ def _configure(options):
     else:
         log.set_global_level(logging.INFO)
 
+    if overlay_path:
+        log.debug(u'overlaying configuration: {0}',
+                  util.displayable_path(overlay_path))
+
     config_path = config.user_config_path()
     if os.path.isfile(config_path):
         log.debug(u'user configuration: {0}',
diff --git a/docs/reference/cli.rst b/docs/reference/cli.rst
index 403c1e174..37fc31767 100644
--- a/docs/reference/cli.rst
+++ b/docs/reference/cli.rst
@@ -72,7 +72,7 @@ box. To extract `rar` files, install the `rarfile`_ package and the
 Optional command flags:
 
 * By default, the command copies files your the library directory and
-  updates the ID3 tags on your music. In order to move the files, instead of 
+  updates the ID3 tags on your music. In order to move the files, instead of
   copying, use the ``-m`` (move) option. If you'd like to leave your music
   files untouched, try the ``-C`` (don't copy) and ``-W`` (don't write tags)
   options. You can also disable this behavior by default in the
@@ -409,7 +409,11 @@ import ...``.
 * ``-v``: verbose mode; prints out a deluge of debugging information. Please use
   this flag when reporting bugs. You can use it twice, as in ``-vv``, to make
   beets even more verbose.
-* ``-c FILE``: read a specified YAML :doc:`configuration file <config>`.
+* ``-c FILE``: read a specified YAML :doc:`configuration file <config>`. This
+  configuration works as an overlay: rather than replacing your normal
+  configuration options entirely, the two are merged. Any individual options set
+  in this config file will override your base configuration.
+
 
 Beets also uses the ``BEETSDIR`` environment variable to look for
 configuration and data.