diff --git a/pymc4/inference/sampling/sample.py b/pymc4/inference/sampling/sample.py
index 588aa369..9c96c3d3 100644
--- a/pymc4/inference/sampling/sample.py
+++ b/pymc4/inference/sampling/sample.py
@@ -9,21 +9,22 @@ def sample(model,  # pylint: disable-msg=too-many-arguments
            step_size=.4,
            num_leapfrog_steps=3,
            numpy=True):
-    initial_state = []
-    for name, (_, shape, _) in model.unobserved.items():
-        initial_state.append(.5 * tf.ones(shape, name="init_{}".format(name)))
+    with model.temp_graph.as_default():
+        initial_state = []
+        for name, (_, shape, _) in model.unobserved.items():
+            initial_state.append(.5 * tf.ones(shape, name="init_{}".format(name)))
 
-    states, kernel_results = tfp.mcmc.sample_chain(
-        num_results=num_results,
-        num_burnin_steps=num_burnin_steps,
-        current_state=initial_state,
-        kernel=tfp.mcmc.HamiltonianMonteCarlo(
-            target_log_prob_fn=model.target_log_prob_fn(),
-            step_size=step_size,
-            num_leapfrog_steps=num_leapfrog_steps))
+        states, kernel_results = tfp.mcmc.sample_chain(
+            num_results=num_results,
+            num_burnin_steps=num_burnin_steps,
+            current_state=initial_state,
+            kernel=tfp.mcmc.HamiltonianMonteCarlo(
+                target_log_prob_fn=model.target_log_prob_fn(),
+                step_size=step_size,
+                num_leapfrog_steps=num_leapfrog_steps))
 
     if numpy:
-        with tf.Session() as sess:
+        with tf.Session(graph=model.temp_graph) as sess:
             states, is_accepted_ = sess.run([states, kernel_results.is_accepted])
             accepted = np.sum(is_accepted_)
             print("Acceptance rate: {}".format(accepted / num_results))
diff --git a/pymc4/model/base.py b/pymc4/model/base.py
index 4c8d1613..40793b63 100644
--- a/pymc4/model/base.py
+++ b/pymc4/model/base.py
@@ -27,7 +27,7 @@ def __getattr__(self, item):
             raise error from e
 
 
-class Model(object):
+class Model():
     def __init__(self, name=None, graph=None, session=None, **config):
         self._cfg = Config(**config)
         self.name = name
@@ -38,6 +38,7 @@ def __init__(self, name=None, graph=None, session=None, **config):
             session = tf.Session(graph=graph)
         self.session = session
         self.observe(**config)
+        self.temp_graph = tf.Graph()
 
     def define(self, f):
         self._f = f
@@ -54,6 +55,7 @@ def _init_variables(self):
         info_collector = interceptors.CollectVariablesInfo()
         with self.graph.as_default(), ed.interception(info_collector):
             self._f(self.cfg)
+        tf.contrib.graph_editor.copy(self.graph, self.temp_graph)
         self._variables = info_collector.result
 
     def test_point(self, sample=True):
@@ -66,12 +68,15 @@ def not_observed(var, *args, **kwargs):  # pylint: disable=unused-argument
             def get_mode(state, rv, *args, **kwargs):  # pylint: disable=unused-argument
                 return rv.distribution.mode()
             chain.insert(0, interceptors.Generic(after=get_mode))
-
-        with self.graph.as_default(), ed.interception(interceptors.Chain(*chain)):
+        tf.contrib.graph_editor.copy(self.graph, self.temp_graph)
+        # pylint: disable=not-context-manager
+        with self.temp_graph.as_default(), ed.interception(interceptors.Chain(*chain)):
             self._f(self.cfg)
-        with self.session.as_default():
-            returns = self.session.run(list(values_collector.result.values()))
-        return dict(zip(values_collector.result.keys(), returns))
+        # pylint: enable=not-context-manager
+        with tf.Session(graph=self.temp_graph) as sess:
+            returns = sess.run(list(values_collector.result.values()))
+        keys = values_collector.result.keys()
+        return dict(zip(keys, returns))
 
     def target_log_prob_fn(self, *args, **kwargs):  # pylint: disable=unused-argument
         """
@@ -83,7 +88,8 @@ def log_joint_fn(*args, **kwargs):  # pylint: disable=unused-argument
             states = dict(zip(self.unobserved.keys(), args))
             states.update(self.observed)
             interceptor = interceptors.CollectLogProb(states)
-            with ed.interception(interceptor):
+            tf.contrib.graph_editor.copy(self.graph, self.temp_graph)
+            with self.temp_graph.as_default(), ed.interception(interceptor):  # pylint: disable=not-context-manager
                 self._f(self._cfg)
 
             log_prob = sum(interceptor.log_probs)
diff --git a/pymc4/util/interceptors.py b/pymc4/util/interceptors.py
index 964d98fe..3172da38 100644
--- a/pymc4/util/interceptors.py
+++ b/pymc4/util/interceptors.py
@@ -12,7 +12,7 @@
 VariableDescription = collections.namedtuple('VariableDescription', 'Dist,shape,rv')
 
 
-class Interceptor(object):
+class Interceptor():
     def name_scope(self):
         return tf.name_scope(self.__class__.__name__.lower())
 
diff --git a/requirements.txt b/requirements.txt
index 2d1cd48c..7b5aaf30 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -2,6 +2,6 @@ xarray==0.10.4
 numpy==1.14.3
 tqdm==4.23.3
 biwrap
-tf-nightly==1.8.0.dev20180331
-tfp-nightly==0.0.1.dev20180515 
-tb-nightly==1.8.0a20180424
+tf-nightly==1.9.0.dev20180607
+tfp-nightly==0.3.0.dev20180725
+tb-nightly==1.9.0a20180613
diff --git a/tests/test_model.py b/tests/test_model.py
index 85c96475..595ad18c 100644
--- a/tests/test_model.py
+++ b/tests/test_model.py
@@ -153,5 +153,5 @@ def simple(cfg):
 
     log_prob_fn = model.target_log_prob_fn()
 
-    with tf.Session():
+    with tf.Session(graph=model.temp_graph):
         assert -0.91893853 == pytest.approx(log_prob_fn(0).eval(), 0.00001)