diff --git a/caffe2/contrib/tensorboard/tensorboard_test.py b/caffe2/contrib/tensorboard/tensorboard_test.py
index 943e75fe1dd0..489be5d43ff2 100644
--- a/caffe2/contrib/tensorboard/tensorboard_test.py
+++ b/caffe2/contrib/tensorboard/tensorboard_test.py
@@ -91,9 +91,11 @@ class TensorboardTest(unittest.TestCase):
         for i, (event, net) in enumerate(zip(events, nets), start=1):
             self.assertEqual(event.step, i)
             self.assertEqual(event.wall_time, i)
-            self.assertEqual(
-                event.graph_def,
-                tb_exporter.nets_to_graph_def([net]).SerializeToString())
+            g = tf.GraphDef()
+            g.ParseFromString(event.graph_def)
+            self.assertMultiLineEqual(
+                str(g),
+                str(tb_exporter.nets_to_graph_def([net])))
 
 
 if __name__ == "__main__":
diff --git a/caffe2/proto/__init__.py b/caffe2/proto/__init__.py
index e69de29bb2d1..a753f26c5380 100644
--- a/caffe2/proto/__init__.py
+++ b/caffe2/proto/__init__.py
@@ -0,0 +1,15 @@
+# NOTE: we have to import python protobuf here **before** we load cpp extension.
+# Otherwise it breaks under certain build conditions if cpp implementation of
+# protobuf is used. Presumably there's some registry in protobuf library and
+# python side has to initialize the dictionary first, before static
+# initialization in python extension does so. Otherwise, duplicated protobuf
+# descriptors will be created and it can lead to obscure errors like
+#   "Parameter to MergeFrom() must be instance of same class:
+#    expected caffe2.NetDef got caffe2.NetDef."
+#
+# This has to be done for all python targets, so listing them here
+from caffe2.proto import caffe2_pb2, metanet_pb2, torch_pb2
+try:
+    from caffe2.caffe2.fb.session.proto import session_pb2
+except ImportError:
+    pass
diff --git a/caffe2/python/_import_c_extension.py b/caffe2/python/_import_c_extension.py
index 4a10d79477d9..dc3e6ea2a2fd 100644
--- a/caffe2/python/_import_c_extension.py
+++ b/caffe2/python/_import_c_extension.py
@@ -5,6 +5,16 @@ import logging
 import sys
 from caffe2.python import extension_loader
 
+# NOTE: we have to import python protobuf here **before** we load cpp extension.
+# Otherwise it breaks under certain build conditions if cpp implementation of
+# protobuf is used. Presumably there's some registry in protobuf library and
+# python side has to initialize the dictionary first, before static
+# initialization in python extension does so. Otherwise, duplicated protobuf
+# descriptors will be created and it can lead to obscure errors like
+#   "Parameter to MergeFrom() must be instance of same class:
+#    expected caffe2.NetDef got caffe2.NetDef."
+import caffe2.proto
+
 # We will first try to load the gpu-enabled caffe2. If it fails, we will then
 # attempt to load the cpu version. The cpu backend is the minimum required, so
 # if that still fails, we will exit loud.
diff --git a/caffe2/python/test/python_protobuf_test.py b/caffe2/python/test/python_protobuf_test.py
new file mode 100644
index 000000000000..817f5e21a563
--- /dev/null
+++ b/caffe2/python/test/python_protobuf_test.py
@@ -0,0 +1,24 @@
+from __future__ import absolute_import
+from __future__ import division
+from __future__ import print_function
+
+# make sure we use cpp implementation of protobuf
+import os
+os.environ["PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION"] = "cpp"
+
+# import cpp extension first
+from caffe2.python import core
+# then import protobuf
+from caffe2.proto import caffe2_pb2, metanet_pb2
+
+import unittest
+
+
+class TestCrossProtoCalls(unittest.TestCase):
+    def testSimple(self):
+        net = caffe2_pb2.NetDef()
+        meta = metanet_pb2.MetaNetDef()
+        # if metanet_pb2 wasn't initialized properly the following fails with a
+        # cryptic message: "Parameter to MergeFrom() must be instance of same
+        # class: expected caffe2.NetDef got caffe2.NetDef."
+        meta.nets.add(key="foo", value=net)