diff --git a/firanka/series/range.py b/firanka/series/range.py
index 25f1ac09405bb4fb73035abf2df12b3f886577be..888845bb721836851d341f88381eaa4218134758 100644
--- a/firanka/series/range.py
+++ b/firanka/series/range.py
@@ -41,7 +41,7 @@ class Range(object):
             args = {
                 True: self.__from_range,
                 False: self.__from_str
-            }[isinstance(rs, type(self))](op)
+            }[isinstance(rs, type(self))](rs)
 
         q = lambda a, b: args[a] and math.isinf(args[b])