theano plactice

>>> import numpy
>>> import theano
>>> import theano.tensor as T
>>> x = T.dscalar()
>>> y = T.dscalar()
>>> c = T.dscalar()
>>> ff = theano.function([c], x*2+y, givens=[(x, c*10), (y,5)])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/xxx/test/larn/local/lib/python2.7/site-packages/theano/compile/function.py", line 223, in function
    profile=profile)
  File "/home/xxx/test/larn/local/lib/python2.7/site-packages/theano/compile/pfunc.py", line 490, in pfunc
    no_default_updates=no_default_updates)
  File "/home/xxx/test/larn/local/lib/python2.7/site-packages/theano/compile/pfunc.py", line 241, in rebuild_collect_shared
    cloned_v = clone_v_get_shared_updates(outputs, copy_inputs_over)
  File "/home/xxx/test/larn/local/lib/python2.7/site-packages/theano/compile/pfunc.py", line 92, in clone_v_get_shared_updates
    clone_a(v.owner, copy_inputs_over)
  File "/home/xxx/test/larn/local/lib/python2.7/site-packages/theano/compile/pfunc.py", line 135, in clone_a
    strict=rebuild_strict)
  File "/home/xxx/test/larn/local/lib/python2.7/site-packages/theano/gof/graph.py", line 213, in clone_with_new_inputs
    new_inputs[i] = curr.type.filter_variable(new)
  File "/home/xxx/test/larn/local/lib/python2.7/site-packages/theano/tensor/type.py", line 205, in filter_variable
    self=self)
TypeError: Cannot convert Type TensorType(int64, scalar) (of Variable <TensorType(int64, scalar)>) into Type TensorType(float64, scalar). You can try to manually convert <TensorType(int64, scalar)> into a TensorType(float64, scalar).
(common)$