diff --git a/bptools/util.py b/bptools/util.py
index 4797930..8c21c41 100644
--- a/bptools/util.py
+++ b/bptools/util.py
@@ -11,6 +11,6 @@ def from_series(cls, s):
         """
         kwargs = {
             attr: value
-            for attr, value in s.items()
+            for attr, value in s.iteritems()
         }
         return cls(**kwargs)