@@ -247,9 +247,9 @@ def astype(self, dtype=None, **kwargs):
         # might be related to numpy ticket # 826
         if not isinstance(ret, type(self)):
             if self.__array_priority__ >= Quantity.__array_priority__:
-                ret = type(self)(ret, self._dimensionality)
+                ret = type(self)(ret, self._dimensionality, dtype=self.dtype)
             else:
-                ret = Quantity(ret, self._dimensionality)
+                ret = Quantity(ret, self._dimensionality, dtype=self.dtype)
 
         return ret
 
 
@@ -38,6 +38,8 @@ def test_rescale(self):
         self.assertTrue(seventyish_km.dtype == np.float32)
         in_meters = seventyish_km.rescale(pq.m)
         self.assertTrue(in_meters.dtype == seventyish_km.dtype)
+        seventyish_km_rescaled_idempotent = seventyish_km.rescale(pq.km)
+        self.assertTrue(seventyish_km_rescaled_idempotent.dtype == np.float32)
 
     def test_set_uncertainty(self):
         a = UncertainQuantity([1, 2], 'm', [.1, .2])