diff --git a/resources/core.py b/resources/core.py
index 46f2cad..55ee6bd 100644
--- a/resources/core.py
+++ b/resources/core.py
@@ -201,7 +201,7 @@ class Interface(object):
             # Assume decorator usage.
 
             def decorator(r):
-                self.map(key, resource=r, collection=is_collection)
+                self.map(key, resource=r, is_collection=is_collection)
                 return r
 
             return decorator