diff --git a/pandas/core/series.py b/pandas/core/series.py
index 626a4a81193cc..6465264df02e3 100644
--- a/pandas/core/series.py
+++ b/pandas/core/series.py
@@ -156,7 +156,11 @@ def __init__(self, data=None, index=None, dtype=None, name=None,
             if data is None:
                 data = {}
             if dtype is not None:
-                dtype = self._validate_dtype(dtype)
+                if dtype is numpy.dtype or dtype is pandas.dtype:
+                    dtype = self._validate_dtype(dtype)
+                else:
+                    raise TypeError("Argument 'dtype' must be
+                                    numpy.dtype or pandas.dtype")
 
             if isinstance(data, MultiIndex):
                 raise NotImplementedError("initializing a Series from a "