diff --git a/src/escpos/capabilities.py b/src/escpos/capabilities.py
index 9ae0e79..3dd5c32 100644
--- a/src/escpos/capabilities.py
+++ b/src/escpos/capabilities.py
@@ -92,11 +92,11 @@ def clean(s):
 # For users, who want to provide their profile
 class Profile(get_profile_class('default')):
 
-    def __init__(self, columns=None, features={}):
+    def __init__(self, columns=None, features=None):
         super(Profile, self).__init__()
 
         self.columns = columns
-        self.features = features
+        self.features = features or {}
 
     def get_columns(self, font):
         if self.columns is not None:
diff --git a/tox.ini b/tox.ini
index b5555cc..362f2a6 100644
--- a/tox.ini
+++ b/tox.ini
@@ -9,7 +9,7 @@ deps = nose
        pytest
        pytest-cov
        hypothesis
-commands = py.test --cov reports
+commands = py.test --cov escpos
 
 [testenv:docs]
 basepython = python