Merge pull request #5878 from bbudescu/rng-floatx

theano/sandbox/rng_mrg.py

@@ -774,15 +774,17 @@ class MRG_RandomStreams(object):
 
         """
         low = as_tensor_variable(low)
-        low = undefined_grad(low)
         high = as_tensor_variable(high)
-        high = undefined_grad(high)
+
         if dtype is None:
             dtype = scal.upcast(config.floatX, low.dtype, high.dtype)
 
         low = cast(low, dtype=dtype)
         high = cast(high, dtype=dtype)
 
+        low = undefined_grad(low)
+        high = undefined_grad(high)
+
         if isinstance(size, tuple):
             msg = "size must be a tuple of int or a Theano variable"
             assert all([isinstance(i, (np.integer, integer_types, Variable))