diff --git a/README.md b/README.md
index 5ed5f53..3307bbd 100644
--- a/README.md
+++ b/README.md
@@ -53,7 +53,7 @@ $ ./bumblebee-status -l themes
 $ ./bumblebee-status -l modules
 ```
 
-Any parameter you can specify with `-p <name>=<value>`, you can alternatively specify in `~/.bumblebee-status.conf` or `~/.config/bumblebee-status.conf`.
+Any parameter you can specify with `-p <name>=<value>`, you can alternatively specify in `~/.bumblebee-status.conf` or `~/.config/bumblebee-status.conf`. This parameters act as a **fallback**, so value specified with `-p` have priority.
 
 Configuration files have a format like this:
 ```
diff --git a/bumblebee/engine.py b/bumblebee/engine.py
index a4e63b8..e08b639 100644
--- a/bumblebee/engine.py
+++ b/bumblebee/engine.py
@@ -43,6 +43,7 @@ class Module(object):
             if os.path.exists(cfg):
                 self._configFile = RawConfigParser()
                 self._configFile.read(cfg)
+                log.debug("reading configuration file {}".format(cfg))
                 break
 
         if self._configFile is not None and self._configFile.has_section("module-parameters"):
@@ -77,9 +78,12 @@ class Module(object):
         """Return the config parameter 'name' for this module"""
         name = "{}.{}".format(self.name, name)
         value = self._config["config"].get(name, default)
+        log.debug("command line parameter {}={}".format(name, str(value)))
         if value == default:
             try:
+                log.debug("trying to read {} from configuration file".format(name))
                 value = self._configFile.get("module-parameters", name)
+                log.debug("configuration file {}={}".format(name, str(value)))
             except:
                 pass
         return value