diff --git a/weboob/backend.py b/weboob/backend.py
index 52dfc977..611684f1 100644
--- a/weboob/backend.py
+++ b/weboob/backend.py
@@ -23,10 +23,7 @@ class Backend:
     def __init__(self, weboob):
         self.weboob = weboob
 
-    def has_caps(self, caps):
-        if not isinstance(caps, (list,tuple)):
-            caps = (caps,)
-
+    def has_caps(self, *caps):
         for c in caps:
             if isinstance(self, c):
                 return True
diff --git a/weboob/frontends/dummy/scripts/dummy b/weboob/frontends/dummy/scripts/dummy
index 4d2edc2d..4d3a4a95 100755
--- a/weboob/frontends/dummy/scripts/dummy
+++ b/weboob/frontends/dummy/scripts/dummy
@@ -33,11 +33,11 @@ class Application(BaseApplication):
         self.weboob.load_modules()
         for name, backend in self.weboob.iter_backends():
             print '= Processing backend name = %s' % name
-            if isinstance(backend, ICapMessages):
+            if backend.has_caps(ICapMessages):
                 print '== Backend is ICapMessages => print its messages'
                 for message in backend.iter_new_messages():
                     print '=== %s' % message
-            if isinstance(backend, ICapMessagesReply):
+            if backend.has_caps(ICapMessagesReply):
                 print '== Backend is ICapMessagesReply => TODO'
 
 if __name__ == '__main__':
diff --git a/weboob/modules.py b/weboob/modules.py
index 5ef0f9e0..3b62a830 100644
--- a/weboob/modules.py
+++ b/weboob/modules.py
@@ -39,10 +39,7 @@ class Module:
         if not self.klass:
             raise ImportError("This is not a backend module (no Backend class found)")
 
-    def has_caps(self, caps):
-        if not isinstance(caps, (list,tuple)):
-            caps = (caps,)
-
+    def has_caps(self, *caps):
         for c in caps:
             if issubclass(self.klass, c):
                 return True