diff --git a/benchmark/addressbook.proto b/benchmark/addressbook.proto
index fc79075..1c08c6b 100644
--- a/benchmark/addressbook.proto
+++ b/benchmark/addressbook.proto
@@ -1,8 +1,11 @@
+syntax = "proto2";
+
 package tutorial;
 
 message Person {
   required string name = 1;
   required int32 id = 2;
+  required string email = 3;
 
   enum PhoneType {
     MOBILE = 0;
@@ -15,7 +18,7 @@ message Person {
     optional PhoneType type = 2 [default = HOME];
   }
 
-  repeated PhoneNumber phone = 3;
+  repeated PhoneNumber phone = 4;
 }
 
 message AddressBook {
diff --git a/benchmark/addressbook_pb2.py b/benchmark/addressbook_pb2.py
index a8e95fe..da203fa 100644
--- a/benchmark/addressbook_pb2.py
+++ b/benchmark/addressbook_pb2.py
@@ -1,19 +1,26 @@
 # Generated by the protocol buffer compiler.  DO NOT EDIT!
 # source: addressbook.proto
 
+import sys
+_b=sys.version_info[0]<3 and (lambda x:x) or (lambda x:x.encode('latin1'))
 from google.protobuf import descriptor as _descriptor
 from google.protobuf import message as _message
 from google.protobuf import reflection as _reflection
+from google.protobuf import symbol_database as _symbol_database
 from google.protobuf import descriptor_pb2
 # @@protoc_insertion_point(imports)
 
+_sym_db = _symbol_database.Default()
+
 
 
 
 DESCRIPTOR = _descriptor.FileDescriptor(
   name='addressbook.proto',
   package='tutorial',
-  serialized_pb='\n\x11\x61\x64\x64ressbook.proto\x12\x08tutorial\"\xda\x01\n\x06Person\x12\x0c\n\x04name\x18\x01 \x02(\t\x12\n\n\x02id\x18\x02 \x02(\x05\x12\r\n\x05\x65mail\x18\x03 \x01(\t\x12+\n\x05phone\x18\x04 \x03(\x0b\x32\x1c.tutorial.Person.PhoneNumber\x1aM\n\x0bPhoneNumber\x12\x0e\n\x06number\x18\x01 \x02(\t\x12.\n\x04type\x18\x02 \x01(\x0e\x32\x1a.tutorial.Person.PhoneType:\x04HOME\"+\n\tPhoneType\x12\n\n\x06MOBILE\x10\x00\x12\x08\n\x04HOME\x10\x01\x12\x08\n\x04WORK\x10\x02\"/\n\x0b\x41\x64\x64ressBook\x12 \n\x06person\x18\x01 \x03(\x0b\x32\x10.tutorial.Person')
+  syntax='proto2',
+  serialized_pb=_b('\n\x11\x61\x64\x64ressbook.proto\x12\x08tutorial\"\xda\x01\n\x06Person\x12\x0c\n\x04name\x18\x01 \x02(\t\x12\n\n\x02id\x18\x02 \x02(\x05\x12\r\n\x05\x65mail\x18\x03 \x02(\t\x12+\n\x05phone\x18\x04 \x03(\x0b\x32\x1c.tutorial.Person.PhoneNumber\x1aM\n\x0bPhoneNumber\x12\x0e\n\x06number\x18\x01 \x02(\t\x12.\n\x04type\x18\x02 \x01(\x0e\x32\x1a.tutorial.Person.PhoneType:\x04HOME\"+\n\tPhoneType\x12\n\n\x06MOBILE\x10\x00\x12\x08\n\x04HOME\x10\x01\x12\x08\n\x04WORK\x10\x02\"/\n\x0b\x41\x64\x64ressBook\x12 \n\x06person\x18\x01 \x03(\x0b\x32\x10.tutorial.Person')
+)
 
 
 
@@ -41,6 +48,7 @@ _PERSON_PHONETYPE = _descriptor.EnumDescriptor(
   serialized_start=207,
   serialized_end=250,
 )
+_sym_db.RegisterEnumDescriptor(_PERSON_PHONETYPE)
 
 
 _PERSON_PHONENUMBER = _descriptor.Descriptor(
@@ -53,7 +61,7 @@ _PERSON_PHONENUMBER = _descriptor.Descriptor(
     _descriptor.FieldDescriptor(
       name='number', full_name='tutorial.Person.PhoneNumber.number', index=0,
       number=1, type=9, cpp_type=9, label=2,
-      has_default_value=False, default_value=unicode("", "utf-8"),
+      has_default_value=False, default_value=_b("").decode('utf-8'),
       message_type=None, enum_type=None, containing_type=None,
       is_extension=False, extension_scope=None,
       options=None),
@@ -72,7 +80,10 @@ _PERSON_PHONENUMBER = _descriptor.Descriptor(
   ],
   options=None,
   is_extendable=False,
+  syntax='proto2',
   extension_ranges=[],
+  oneofs=[
+  ],
   serialized_start=128,
   serialized_end=205,
 )
@@ -87,7 +98,7 @@ _PERSON = _descriptor.Descriptor(
     _descriptor.FieldDescriptor(
       name='name', full_name='tutorial.Person.name', index=0,
       number=1, type=9, cpp_type=9, label=2,
-      has_default_value=False, default_value=unicode("", "utf-8"),
+      has_default_value=False, default_value=_b("").decode('utf-8'),
       message_type=None, enum_type=None, containing_type=None,
       is_extension=False, extension_scope=None,
       options=None),
@@ -100,8 +111,8 @@ _PERSON = _descriptor.Descriptor(
       options=None),
     _descriptor.FieldDescriptor(
       name='email', full_name='tutorial.Person.email', index=2,
-      number=3, type=9, cpp_type=9, label=1,
-      has_default_value=False, default_value=unicode("", "utf-8"),
+      number=3, type=9, cpp_type=9, label=2,
+      has_default_value=False, default_value=_b("").decode('utf-8'),
       message_type=None, enum_type=None, containing_type=None,
       is_extension=False, extension_scope=None,
       options=None),
@@ -121,7 +132,10 @@ _PERSON = _descriptor.Descriptor(
   ],
   options=None,
   is_extendable=False,
+  syntax='proto2',
   extension_ranges=[],
+  oneofs=[
+  ],
   serialized_start=32,
   serialized_end=250,
 )
@@ -149,36 +163,44 @@ _ADDRESSBOOK = _descriptor.Descriptor(
   ],
   options=None,
   is_extendable=False,
+  syntax='proto2',
   extension_ranges=[],
+  oneofs=[
+  ],
   serialized_start=252,
   serialized_end=299,
 )
 
 _PERSON_PHONENUMBER.fields_by_name['type'].enum_type = _PERSON_PHONETYPE
-_PERSON_PHONENUMBER.containing_type = _PERSON;
+_PERSON_PHONENUMBER.containing_type = _PERSON
 _PERSON.fields_by_name['phone'].message_type = _PERSON_PHONENUMBER
-_PERSON_PHONETYPE.containing_type = _PERSON;
+_PERSON_PHONETYPE.containing_type = _PERSON
 _ADDRESSBOOK.fields_by_name['person'].message_type = _PERSON
 DESCRIPTOR.message_types_by_name['Person'] = _PERSON
 DESCRIPTOR.message_types_by_name['AddressBook'] = _ADDRESSBOOK
+_sym_db.RegisterFileDescriptor(DESCRIPTOR)
 
-class Person(_message.Message):
-  __metaclass__ = _reflection.GeneratedProtocolMessageType
-
-  class PhoneNumber(_message.Message):
-    __metaclass__ = _reflection.GeneratedProtocolMessageType
-    DESCRIPTOR = _PERSON_PHONENUMBER
+Person = _reflection.GeneratedProtocolMessageType('Person', (_message.Message,), dict(
 
+  PhoneNumber = _reflection.GeneratedProtocolMessageType('PhoneNumber', (_message.Message,), dict(
+    DESCRIPTOR = _PERSON_PHONENUMBER,
+    __module__ = 'addressbook_pb2'
     # @@protoc_insertion_point(class_scope:tutorial.Person.PhoneNumber)
-  DESCRIPTOR = _PERSON
-
+    ))
+  ,
+  DESCRIPTOR = _PERSON,
+  __module__ = 'addressbook_pb2'
   # @@protoc_insertion_point(class_scope:tutorial.Person)
+  ))
+_sym_db.RegisterMessage(Person)
+_sym_db.RegisterMessage(Person.PhoneNumber)
 
-class AddressBook(_message.Message):
-  __metaclass__ = _reflection.GeneratedProtocolMessageType
-  DESCRIPTOR = _ADDRESSBOOK
-
+AddressBook = _reflection.GeneratedProtocolMessageType('AddressBook', (_message.Message,), dict(
+  DESCRIPTOR = _ADDRESSBOOK,
+  __module__ = 'addressbook_pb2'
   # @@protoc_insertion_point(class_scope:tutorial.AddressBook)
+  ))
+_sym_db.RegisterMessage(AddressBook)
 
 
 # @@protoc_insertion_point(module_scope)
diff --git a/benchmark/bin/run_all.py b/benchmark/bin/run_all.py
index 60421a0..c3458d9 100755
--- a/benchmark/bin/run_all.py
+++ b/benchmark/bin/run_all.py
@@ -39,7 +39,7 @@ def run_one(prefix, name, mode, iters, faster, compression):
     data = {}
 
     if p.returncode != 0:
-        sys.stderr.write(' '.join(command) + ' failed to run with errors: \n' + p.stderr.read() + '\n')
+        sys.stderr.write(' '.join(command) + ' failed to run with errors: \n' + p.stderr.read().decode(sys.stdout.encoding) + '\n')
         sys.stderr.flush()
 
     data['type'] = res_type
diff --git a/benchmark/carsales.proto b/benchmark/carsales.proto
index 5ec587e..0b6a975 100644
--- a/benchmark/carsales.proto
+++ b/benchmark/carsales.proto
@@ -21,6 +21,8 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+syntax = "proto2";
+
 package capnp.benchmark.protobuf;
 
 message ParkingLot {
diff --git a/benchmark/carsales_pb2.py b/benchmark/carsales_pb2.py
index 2cd533a..7c73539 100644
--- a/benchmark/carsales_pb2.py
+++ b/benchmark/carsales_pb2.py
@@ -1,20 +1,27 @@
 # Generated by the protocol buffer compiler.  DO NOT EDIT!
 # source: carsales.proto
 
+import sys
+_b=sys.version_info[0]<3 and (lambda x:x) or (lambda x:x.encode('latin1'))
 from google.protobuf.internal import enum_type_wrapper
 from google.protobuf import descriptor as _descriptor
 from google.protobuf import message as _message
 from google.protobuf import reflection as _reflection
+from google.protobuf import symbol_database as _symbol_database
 from google.protobuf import descriptor_pb2
 # @@protoc_insertion_point(imports)
 
+_sym_db = _symbol_database.Default()
+
 
 
 
 DESCRIPTOR = _descriptor.FileDescriptor(
   name='carsales.proto',
   package='capnp.benchmark.protobuf',
-  serialized_pb='\n\x0e\x63\x61rsales.proto\x12\x18\x63\x61pnp.benchmark.protobuf\"8\n\nParkingLot\x12*\n\x03\x63\x61r\x18\x01 \x03(\x0b\x32\x1d.capnp.benchmark.protobuf.Car\"\x1c\n\nTotalValue\x12\x0e\n\x06\x61mount\x18\x01 \x02(\x04\"\xbc\x03\n\x03\x43\x61r\x12\x0c\n\x04make\x18\x01 \x01(\t\x12\r\n\x05model\x18\x02 \x01(\t\x12.\n\x05\x63olor\x18\x03 \x01(\x0e\x32\x1f.capnp.benchmark.protobuf.Color\x12\r\n\x05seats\x18\x04 \x01(\r\x12\r\n\x05\x64oors\x18\x05 \x01(\r\x12.\n\x05wheel\x18\x06 \x03(\x0b\x32\x1f.capnp.benchmark.protobuf.Wheel\x12\x0e\n\x06length\x18\x07 \x01(\r\x12\r\n\x05width\x18\x08 \x01(\r\x12\x0e\n\x06height\x18\t \x01(\r\x12\x0e\n\x06weight\x18\n \x01(\r\x12\x30\n\x06\x65ngine\x18\x0b \x01(\x0b\x32 .capnp.benchmark.protobuf.Engine\x12\x15\n\rfuel_capacity\x18\x0c \x01(\x02\x12\x12\n\nfuel_level\x18\r \x01(\x02\x12\x19\n\x11has_power_windows\x18\x0e \x01(\x08\x12\x1a\n\x12has_power_steering\x18\x0f \x01(\x08\x12\x1a\n\x12has_cruise_control\x18\x10 \x01(\x08\x12\x13\n\x0b\x63up_holders\x18\x11 \x01(\r\x12\x16\n\x0ehas_nav_system\x18\x12 \x01(\x08\"C\n\x05Wheel\x12\x10\n\x08\x64iameter\x18\x01 \x01(\r\x12\x14\n\x0c\x61ir_pressure\x18\x02 \x01(\x02\x12\x12\n\nsnow_tires\x18\x03 \x01(\x08\"d\n\x06\x45ngine\x12\x12\n\nhorsepower\x18\x01 \x01(\r\x12\x11\n\tcylinders\x18\x02 \x01(\r\x12\n\n\x02\x63\x63\x18\x03 \x01(\r\x12\x10\n\x08uses_gas\x18\x04 \x01(\x08\x12\x15\n\ruses_electric\x18\x05 \x01(\x08*j\n\x05\x43olor\x12\t\n\x05\x42LACK\x10\x00\x12\t\n\x05WHITE\x10\x01\x12\x07\n\x03RED\x10\x02\x12\t\n\x05GREEN\x10\x03\x12\x08\n\x04\x42LUE\x10\x04\x12\x08\n\x04\x43YAN\x10\x05\x12\x0b\n\x07MAGENTA\x10\x06\x12\n\n\x06YELLOW\x10\x07\x12\n\n\x06SILVER\x10\x08')
+  syntax='proto2',
+  serialized_pb=_b('\n\x0e\x63\x61rsales.proto\x12\x18\x63\x61pnp.benchmark.protobuf\"8\n\nParkingLot\x12*\n\x03\x63\x61r\x18\x01 \x03(\x0b\x32\x1d.capnp.benchmark.protobuf.Car\"\x1c\n\nTotalValue\x12\x0e\n\x06\x61mount\x18\x01 \x02(\x04\"\xbc\x03\n\x03\x43\x61r\x12\x0c\n\x04make\x18\x01 \x01(\t\x12\r\n\x05model\x18\x02 \x01(\t\x12.\n\x05\x63olor\x18\x03 \x01(\x0e\x32\x1f.capnp.benchmark.protobuf.Color\x12\r\n\x05seats\x18\x04 \x01(\r\x12\r\n\x05\x64oors\x18\x05 \x01(\r\x12.\n\x05wheel\x18\x06 \x03(\x0b\x32\x1f.capnp.benchmark.protobuf.Wheel\x12\x0e\n\x06length\x18\x07 \x01(\r\x12\r\n\x05width\x18\x08 \x01(\r\x12\x0e\n\x06height\x18\t \x01(\r\x12\x0e\n\x06weight\x18\n \x01(\r\x12\x30\n\x06\x65ngine\x18\x0b \x01(\x0b\x32 .capnp.benchmark.protobuf.Engine\x12\x15\n\rfuel_capacity\x18\x0c \x01(\x02\x12\x12\n\nfuel_level\x18\r \x01(\x02\x12\x19\n\x11has_power_windows\x18\x0e \x01(\x08\x12\x1a\n\x12has_power_steering\x18\x0f \x01(\x08\x12\x1a\n\x12has_cruise_control\x18\x10 \x01(\x08\x12\x13\n\x0b\x63up_holders\x18\x11 \x01(\r\x12\x16\n\x0ehas_nav_system\x18\x12 \x01(\x08\"C\n\x05Wheel\x12\x10\n\x08\x64iameter\x18\x01 \x01(\r\x12\x14\n\x0c\x61ir_pressure\x18\x02 \x01(\x02\x12\x12\n\nsnow_tires\x18\x03 \x01(\x08\"d\n\x06\x45ngine\x12\x12\n\nhorsepower\x18\x01 \x01(\r\x12\x11\n\tcylinders\x18\x02 \x01(\r\x12\n\n\x02\x63\x63\x18\x03 \x01(\r\x12\x10\n\x08uses_gas\x18\x04 \x01(\x08\x12\x15\n\ruses_electric\x18\x05 \x01(\x08*j\n\x05\x43olor\x12\t\n\x05\x42LACK\x10\x00\x12\t\n\x05WHITE\x10\x01\x12\x07\n\x03RED\x10\x02\x12\t\n\x05GREEN\x10\x03\x12\x08\n\x04\x42LUE\x10\x04\x12\x08\n\x04\x43YAN\x10\x05\x12\x0b\n\x07MAGENTA\x10\x06\x12\n\n\x06YELLOW\x10\x07\x12\n\n\x06SILVER\x10\x08')
+)
 
 _COLOR = _descriptor.EnumDescriptor(
   name='Color',
@@ -64,6 +71,7 @@ _COLOR = _descriptor.EnumDescriptor(
   serialized_start=750,
   serialized_end=856,
 )
+_sym_db.RegisterEnumDescriptor(_COLOR)
 
 Color = enum_type_wrapper.EnumTypeWrapper(_COLOR)
 BLACK = 0
@@ -100,7 +108,10 @@ _PARKINGLOT = _descriptor.Descriptor(
   ],
   options=None,
   is_extendable=False,
+  syntax='proto2',
   extension_ranges=[],
+  oneofs=[
+  ],
   serialized_start=44,
   serialized_end=100,
 )
@@ -128,7 +139,10 @@ _TOTALVALUE = _descriptor.Descriptor(
   ],
   options=None,
   is_extendable=False,
+  syntax='proto2',
   extension_ranges=[],
+  oneofs=[
+  ],
   serialized_start=102,
   serialized_end=130,
 )
@@ -144,14 +158,14 @@ _CAR = _descriptor.Descriptor(
     _descriptor.FieldDescriptor(
       name='make', full_name='capnp.benchmark.protobuf.Car.make', index=0,
       number=1, type=9, cpp_type=9, label=1,
-      has_default_value=False, default_value=unicode("", "utf-8"),
+      has_default_value=False, default_value=_b("").decode('utf-8'),
       message_type=None, enum_type=None, containing_type=None,
       is_extension=False, extension_scope=None,
       options=None),
     _descriptor.FieldDescriptor(
       name='model', full_name='capnp.benchmark.protobuf.Car.model', index=1,
       number=2, type=9, cpp_type=9, label=1,
-      has_default_value=False, default_value=unicode("", "utf-8"),
+      has_default_value=False, default_value=_b("").decode('utf-8'),
       message_type=None, enum_type=None, containing_type=None,
       is_extension=False, extension_scope=None,
       options=None),
@@ -221,14 +235,14 @@ _CAR = _descriptor.Descriptor(
     _descriptor.FieldDescriptor(
       name='fuel_capacity', full_name='capnp.benchmark.protobuf.Car.fuel_capacity', index=11,
       number=12, type=2, cpp_type=6, label=1,
-      has_default_value=False, default_value=0,
+      has_default_value=False, default_value=float(0),
       message_type=None, enum_type=None, containing_type=None,
       is_extension=False, extension_scope=None,
       options=None),
     _descriptor.FieldDescriptor(
       name='fuel_level', full_name='capnp.benchmark.protobuf.Car.fuel_level', index=12,
       number=13, type=2, cpp_type=6, label=1,
-      has_default_value=False, default_value=0,
+      has_default_value=False, default_value=float(0),
       message_type=None, enum_type=None, containing_type=None,
       is_extension=False, extension_scope=None,
       options=None),
@@ -275,7 +289,10 @@ _CAR = _descriptor.Descriptor(
   ],
   options=None,
   is_extendable=False,
+  syntax='proto2',
   extension_ranges=[],
+  oneofs=[
+  ],
   serialized_start=133,
   serialized_end=577,
 )
@@ -298,7 +315,7 @@ _WHEEL = _descriptor.Descriptor(
     _descriptor.FieldDescriptor(
       name='air_pressure', full_name='capnp.benchmark.protobuf.Wheel.air_pressure', index=1,
       number=2, type=2, cpp_type=6, label=1,
-      has_default_value=False, default_value=0,
+      has_default_value=False, default_value=float(0),
       message_type=None, enum_type=None, containing_type=None,
       is_extension=False, extension_scope=None,
       options=None),
@@ -317,7 +334,10 @@ _WHEEL = _descriptor.Descriptor(
   ],
   options=None,
   is_extendable=False,
+  syntax='proto2',
   extension_ranges=[],
+  oneofs=[
+  ],
   serialized_start=579,
   serialized_end=646,
 )
@@ -373,7 +393,10 @@ _ENGINE = _descriptor.Descriptor(
   ],
   options=None,
   is_extendable=False,
+  syntax='proto2',
   extension_ranges=[],
+  oneofs=[
+  ],
   serialized_start=648,
   serialized_end=748,
 )
@@ -387,36 +410,43 @@ DESCRIPTOR.message_types_by_name['TotalValue'] = _TOTALVALUE
 DESCRIPTOR.message_types_by_name['Car'] = _CAR
 DESCRIPTOR.message_types_by_name['Wheel'] = _WHEEL
 DESCRIPTOR.message_types_by_name['Engine'] = _ENGINE
+DESCRIPTOR.enum_types_by_name['Color'] = _COLOR
+_sym_db.RegisterFileDescriptor(DESCRIPTOR)
 
-class ParkingLot(_message.Message):
-  __metaclass__ = _reflection.GeneratedProtocolMessageType
-  DESCRIPTOR = _PARKINGLOT
-
+ParkingLot = _reflection.GeneratedProtocolMessageType('ParkingLot', (_message.Message,), dict(
+  DESCRIPTOR = _PARKINGLOT,
+  __module__ = 'carsales_pb2'
   # @@protoc_insertion_point(class_scope:capnp.benchmark.protobuf.ParkingLot)
+  ))
+_sym_db.RegisterMessage(ParkingLot)
 
-class TotalValue(_message.Message):
-  __metaclass__ = _reflection.GeneratedProtocolMessageType
-  DESCRIPTOR = _TOTALVALUE
-
+TotalValue = _reflection.GeneratedProtocolMessageType('TotalValue', (_message.Message,), dict(
+  DESCRIPTOR = _TOTALVALUE,
+  __module__ = 'carsales_pb2'
   # @@protoc_insertion_point(class_scope:capnp.benchmark.protobuf.TotalValue)
+  ))
+_sym_db.RegisterMessage(TotalValue)
 
-class Car(_message.Message):
-  __metaclass__ = _reflection.GeneratedProtocolMessageType
-  DESCRIPTOR = _CAR
-
+Car = _reflection.GeneratedProtocolMessageType('Car', (_message.Message,), dict(
+  DESCRIPTOR = _CAR,
+  __module__ = 'carsales_pb2'
   # @@protoc_insertion_point(class_scope:capnp.benchmark.protobuf.Car)
+  ))
+_sym_db.RegisterMessage(Car)
 
-class Wheel(_message.Message):
-  __metaclass__ = _reflection.GeneratedProtocolMessageType
-  DESCRIPTOR = _WHEEL
-
+Wheel = _reflection.GeneratedProtocolMessageType('Wheel', (_message.Message,), dict(
+  DESCRIPTOR = _WHEEL,
+  __module__ = 'carsales_pb2'
   # @@protoc_insertion_point(class_scope:capnp.benchmark.protobuf.Wheel)
+  ))
+_sym_db.RegisterMessage(Wheel)
 
-class Engine(_message.Message):
-  __metaclass__ = _reflection.GeneratedProtocolMessageType
-  DESCRIPTOR = _ENGINE
-
+Engine = _reflection.GeneratedProtocolMessageType('Engine', (_message.Message,), dict(
+  DESCRIPTOR = _ENGINE,
+  __module__ = 'carsales_pb2'
   # @@protoc_insertion_point(class_scope:capnp.benchmark.protobuf.Engine)
+  ))
+_sym_db.RegisterMessage(Engine)
 
 
 # @@protoc_insertion_point(module_scope)
diff --git a/benchmark/carsales_proto.py b/benchmark/carsales_proto.py
index 5bdcd17..c969070 100755
--- a/benchmark/carsales_proto.py
+++ b/benchmark/carsales_proto.py
@@ -25,7 +25,7 @@ def random_car(car):
     car.length = 170 + rand_int(150)
     car.width = 48 + rand_int(36)
     car.height = 54 + rand_int(48)
-    car.weight = car.length * car.width * car.height / 200
+    car.weight = car.length * car.width * car.height // 200
 
     engine = car.engine
     engine.horsepower = 100 * rand_int(400)
@@ -51,7 +51,7 @@ def calc_value(car):
         result += wheel.diameter * wheel.diameter
         result += 100 if wheel.snow_tires else 0
 
-    result += car.length * car.width * car.height / 50
+    result += car.length * car.width * car.height // 50
 
     engine = car.engine
     result += engine.horsepower * 40
diff --git a/benchmark/carsales_pycapnp.py b/benchmark/carsales_pycapnp.py
index c545f8a..d6ed6f2 100755
--- a/benchmark/carsales_pycapnp.py
+++ b/benchmark/carsales_pycapnp.py
@@ -25,7 +25,7 @@ def random_car(car):
     car.length = 170 + rand_int(150)
     car.width = 48 + rand_int(36)
     car.height = 54 + rand_int(48)
-    car.weight = car.length * car.width * car.height / 200
+    car.weight = car.length * car.width * car.height // 200
 
     engine = car.init('engine')
     engine.horsepower = 100 * rand_int(400)
@@ -51,7 +51,7 @@ def calc_value(car):
         result += wheel.diameter * wheel.diameter
         result += 100 if wheel.snowTires else 0
 
-    result += car.length * car.width * car.height / 50
+    result += car.length * car.width * car.height // 50
 
     engine = car.engine
     result += engine.horsepower * 40
diff --git a/benchmark/catrank.proto b/benchmark/catrank.proto
index 87f2cf8..c3f55ae 100644
--- a/benchmark/catrank.proto
+++ b/benchmark/catrank.proto
@@ -21,6 +21,8 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+syntax = "proto2";
+
 package capnp.benchmark.protobuf;
 
 message SearchResultList {
diff --git a/benchmark/catrank_pb2.py b/benchmark/catrank_pb2.py
index 1baf3b0..3bdf2e6 100644
--- a/benchmark/catrank_pb2.py
+++ b/benchmark/catrank_pb2.py
@@ -1,19 +1,26 @@
 # Generated by the protocol buffer compiler.  DO NOT EDIT!
 # source: catrank.proto
 
+import sys
+_b=sys.version_info[0]<3 and (lambda x:x) or (lambda x:x.encode('latin1'))
 from google.protobuf import descriptor as _descriptor
 from google.protobuf import message as _message
 from google.protobuf import reflection as _reflection
+from google.protobuf import symbol_database as _symbol_database
 from google.protobuf import descriptor_pb2
 # @@protoc_insertion_point(imports)
 
+_sym_db = _symbol_database.Default()
+
 
 
 
 DESCRIPTOR = _descriptor.FileDescriptor(
   name='catrank.proto',
   package='capnp.benchmark.protobuf',
-  serialized_pb='\n\rcatrank.proto\x12\x18\x63\x61pnp.benchmark.protobuf\"J\n\x10SearchResultList\x12\x36\n\x06result\x18\x01 \x03(\x0b\x32&.capnp.benchmark.protobuf.SearchResult\";\n\x0cSearchResult\x12\x0b\n\x03url\x18\x01 \x01(\t\x12\r\n\x05score\x18\x02 \x01(\x01\x12\x0f\n\x07snippet\x18\x03 \x01(\t')
+  syntax='proto2',
+  serialized_pb=_b('\n\rcatrank.proto\x12\x18\x63\x61pnp.benchmark.protobuf\"J\n\x10SearchResultList\x12\x36\n\x06result\x18\x01 \x03(\x0b\x32&.capnp.benchmark.protobuf.SearchResult\";\n\x0cSearchResult\x12\x0b\n\x03url\x18\x01 \x01(\t\x12\r\n\x05score\x18\x02 \x01(\x01\x12\x0f\n\x07snippet\x18\x03 \x01(\t')
+)
 
 
 
@@ -40,7 +47,10 @@ _SEARCHRESULTLIST = _descriptor.Descriptor(
   ],
   options=None,
   is_extendable=False,
+  syntax='proto2',
   extension_ranges=[],
+  oneofs=[
+  ],
   serialized_start=43,
   serialized_end=117,
 )
@@ -56,21 +66,21 @@ _SEARCHRESULT = _descriptor.Descriptor(
     _descriptor.FieldDescriptor(
       name='url', full_name='capnp.benchmark.protobuf.SearchResult.url', index=0,
       number=1, type=9, cpp_type=9, label=1,
-      has_default_value=False, default_value=unicode("", "utf-8"),
+      has_default_value=False, default_value=_b("").decode('utf-8'),
       message_type=None, enum_type=None, containing_type=None,
       is_extension=False, extension_scope=None,
       options=None),
     _descriptor.FieldDescriptor(
       name='score', full_name='capnp.benchmark.protobuf.SearchResult.score', index=1,
       number=2, type=1, cpp_type=5, label=1,
-      has_default_value=False, default_value=0,
+      has_default_value=False, default_value=float(0),
       message_type=None, enum_type=None, containing_type=None,
       is_extension=False, extension_scope=None,
       options=None),
     _descriptor.FieldDescriptor(
       name='snippet', full_name='capnp.benchmark.protobuf.SearchResult.snippet', index=2,
       number=3, type=9, cpp_type=9, label=1,
-      has_default_value=False, default_value=unicode("", "utf-8"),
+      has_default_value=False, default_value=_b("").decode('utf-8'),
       message_type=None, enum_type=None, containing_type=None,
       is_extension=False, extension_scope=None,
       options=None),
@@ -82,7 +92,10 @@ _SEARCHRESULT = _descriptor.Descriptor(
   ],
   options=None,
   is_extendable=False,
+  syntax='proto2',
   extension_ranges=[],
+  oneofs=[
+  ],
   serialized_start=119,
   serialized_end=178,
 )
@@ -90,18 +103,21 @@ _SEARCHRESULT = _descriptor.Descriptor(
 _SEARCHRESULTLIST.fields_by_name['result'].message_type = _SEARCHRESULT
 DESCRIPTOR.message_types_by_name['SearchResultList'] = _SEARCHRESULTLIST
 DESCRIPTOR.message_types_by_name['SearchResult'] = _SEARCHRESULT
+_sym_db.RegisterFileDescriptor(DESCRIPTOR)
 
-class SearchResultList(_message.Message):
-  __metaclass__ = _reflection.GeneratedProtocolMessageType
-  DESCRIPTOR = _SEARCHRESULTLIST
-
+SearchResultList = _reflection.GeneratedProtocolMessageType('SearchResultList', (_message.Message,), dict(
+  DESCRIPTOR = _SEARCHRESULTLIST,
+  __module__ = 'catrank_pb2'
   # @@protoc_insertion_point(class_scope:capnp.benchmark.protobuf.SearchResultList)
+  ))
+_sym_db.RegisterMessage(SearchResultList)
 
-class SearchResult(_message.Message):
-  __metaclass__ = _reflection.GeneratedProtocolMessageType
-  DESCRIPTOR = _SEARCHRESULT
-
+SearchResult = _reflection.GeneratedProtocolMessageType('SearchResult', (_message.Message,), dict(
+  DESCRIPTOR = _SEARCHRESULT,
+  __module__ = 'catrank_pb2'
   # @@protoc_insertion_point(class_scope:capnp.benchmark.protobuf.SearchResult)
+  ))
+_sym_db.RegisterMessage(SearchResult)
 
 
 # @@protoc_insertion_point(module_scope)
diff --git a/benchmark/catrank_proto.py b/benchmark/catrank_proto.py
index d91822e..7658d41 100755
--- a/benchmark/catrank_proto.py
+++ b/benchmark/catrank_proto.py
@@ -2,8 +2,12 @@
 
 from common import rand_int, rand_double, rand_bool, WORDS, from_bytes_helper
 from random import choice
-from string import letters
-from itertools import izip
+from string import ascii_letters
+try:
+  # Python 2
+  from itertools import izip
+except ImportError:
+  izip = zip
 import catrank_pb2
 
 class Benchmark:
@@ -22,7 +26,7 @@ class Benchmark:
             result = request.result.add()
             result.score = 1000 - i
             url_size = rand_int(100)
-            result.url = "http://example.com/" + ''.join([choice(letters) for _ in range(url_size)])
+            result.url = "http://example.com/" + ''.join([choice(ascii_letters) for _ in range(url_size)])
 
             isCat = rand_bool()
             isDog = rand_bool()
diff --git a/benchmark/catrank_pycapnp.py b/benchmark/catrank_pycapnp.py
index a1cb67a..6977fe3 100755
--- a/benchmark/catrank_pycapnp.py
+++ b/benchmark/catrank_pycapnp.py
@@ -4,8 +4,12 @@ import capnp
 import catrank_capnp
 from common import rand_int, rand_double, rand_bool, WORDS
 from random import choice
-from string import letters
-from itertools import izip
+from string import ascii_letters
+try:
+  # Python 2
+  from itertools import izip
+except ImportError:
+  izip = zip
 
 class Benchmark:
     def __init__(self, compression):
@@ -29,7 +33,7 @@ class Benchmark:
         for i, result in enumerate(results):
             result.score = 1000 - i
             url_size = rand_int(100)
-            result.url = "http://example.com/" + ''.join([choice(letters) for _ in range(url_size)])
+            result.url = "http://example.com/" + ''.join([choice(ascii_letters) for _ in range(url_size)])
 
             isCat = rand_bool()
             isDog = rand_bool()
diff --git a/benchmark/eval.proto b/benchmark/eval.proto
index 4c6f72c..204a081 100644
--- a/benchmark/eval.proto
+++ b/benchmark/eval.proto
@@ -21,6 +21,8 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+syntax = "proto2";
+
 package capnp.benchmark.protobuf;
 
 enum Operation {
diff --git a/benchmark/eval_pb2.py b/benchmark/eval_pb2.py
index e2848f0..b3dae75 100644
--- a/benchmark/eval_pb2.py
+++ b/benchmark/eval_pb2.py
@@ -1,20 +1,27 @@
 # Generated by the protocol buffer compiler.  DO NOT EDIT!
 # source: eval.proto
 
+import sys
+_b=sys.version_info[0]<3 and (lambda x:x) or (lambda x:x.encode('latin1'))
 from google.protobuf.internal import enum_type_wrapper
 from google.protobuf import descriptor as _descriptor
 from google.protobuf import message as _message
 from google.protobuf import reflection as _reflection
+from google.protobuf import symbol_database as _symbol_database
 from google.protobuf import descriptor_pb2
 # @@protoc_insertion_point(imports)
 
+_sym_db = _symbol_database.Default()
+
 
 
 
 DESCRIPTOR = _descriptor.FileDescriptor(
   name='eval.proto',
   package='capnp.benchmark.protobuf',
-  serialized_pb='\n\neval.proto\x12\x18\x63\x61pnp.benchmark.protobuf\"\xe5\x01\n\nExpression\x12/\n\x02op\x18\x01 \x02(\x0e\x32#.capnp.benchmark.protobuf.Operation\x12\x12\n\nleft_value\x18\x02 \x01(\x05\x12=\n\x0fleft_expression\x18\x03 \x01(\x0b\x32$.capnp.benchmark.protobuf.Expression\x12\x13\n\x0bright_value\x18\x04 \x01(\x05\x12>\n\x10right_expression\x18\x05 \x01(\x0b\x32$.capnp.benchmark.protobuf.Expression\"!\n\x10\x45valuationResult\x12\r\n\x05value\x18\x01 \x02(\x11*I\n\tOperation\x12\x07\n\x03\x41\x44\x44\x10\x00\x12\x0c\n\x08SUBTRACT\x10\x01\x12\x0c\n\x08MULTIPLY\x10\x02\x12\n\n\x06\x44IVIDE\x10\x03\x12\x0b\n\x07MODULUS\x10\x04')
+  syntax='proto2',
+  serialized_pb=_b('\n\neval.proto\x12\x18\x63\x61pnp.benchmark.protobuf\"\xe5\x01\n\nExpression\x12/\n\x02op\x18\x01 \x02(\x0e\x32#.capnp.benchmark.protobuf.Operation\x12\x12\n\nleft_value\x18\x02 \x01(\x05\x12=\n\x0fleft_expression\x18\x03 \x01(\x0b\x32$.capnp.benchmark.protobuf.Expression\x12\x13\n\x0bright_value\x18\x04 \x01(\x05\x12>\n\x10right_expression\x18\x05 \x01(\x0b\x32$.capnp.benchmark.protobuf.Expression\"!\n\x10\x45valuationResult\x12\r\n\x05value\x18\x01 \x02(\x11*I\n\tOperation\x12\x07\n\x03\x41\x44\x44\x10\x00\x12\x0c\n\x08SUBTRACT\x10\x01\x12\x0c\n\x08MULTIPLY\x10\x02\x12\n\n\x06\x44IVIDE\x10\x03\x12\x0b\n\x07MODULUS\x10\x04')
+)
 
 _OPERATION = _descriptor.EnumDescriptor(
   name='Operation',
@@ -48,6 +55,7 @@ _OPERATION = _descriptor.EnumDescriptor(
   serialized_start=307,
   serialized_end=380,
 )
+_sym_db.RegisterEnumDescriptor(_OPERATION)
 
 Operation = enum_type_wrapper.EnumTypeWrapper(_OPERATION)
 ADD = 0
@@ -108,7 +116,10 @@ _EXPRESSION = _descriptor.Descriptor(
   ],
   options=None,
   is_extendable=False,
+  syntax='proto2',
   extension_ranges=[],
+  oneofs=[
+  ],
   serialized_start=41,
   serialized_end=270,
 )
@@ -136,7 +147,10 @@ _EVALUATIONRESULT = _descriptor.Descriptor(
   ],
   options=None,
   is_extendable=False,
+  syntax='proto2',
   extension_ranges=[],
+  oneofs=[
+  ],
   serialized_start=272,
   serialized_end=305,
 )
@@ -146,18 +160,22 @@ _EXPRESSION.fields_by_name['left_expression'].message_type = _EXPRESSION
 _EXPRESSION.fields_by_name['right_expression'].message_type = _EXPRESSION
 DESCRIPTOR.message_types_by_name['Expression'] = _EXPRESSION
 DESCRIPTOR.message_types_by_name['EvaluationResult'] = _EVALUATIONRESULT
+DESCRIPTOR.enum_types_by_name['Operation'] = _OPERATION
+_sym_db.RegisterFileDescriptor(DESCRIPTOR)
 
-class Expression(_message.Message):
-  __metaclass__ = _reflection.GeneratedProtocolMessageType
-  DESCRIPTOR = _EXPRESSION
-
+Expression = _reflection.GeneratedProtocolMessageType('Expression', (_message.Message,), dict(
+  DESCRIPTOR = _EXPRESSION,
+  __module__ = 'eval_pb2'
   # @@protoc_insertion_point(class_scope:capnp.benchmark.protobuf.Expression)
+  ))
+_sym_db.RegisterMessage(Expression)
 
-class EvaluationResult(_message.Message):
-  __metaclass__ = _reflection.GeneratedProtocolMessageType
-  DESCRIPTOR = _EVALUATIONRESULT
-
+EvaluationResult = _reflection.GeneratedProtocolMessageType('EvaluationResult', (_message.Message,), dict(
+  DESCRIPTOR = _EVALUATIONRESULT,
+  __module__ = 'eval_pb2'
   # @@protoc_insertion_point(class_scope:capnp.benchmark.protobuf.EvaluationResult)
+  ))
+_sym_db.RegisterMessage(EvaluationResult)
 
 
 # @@protoc_insertion_point(module_scope)
diff --git a/benchmark/eval_proto.py b/benchmark/eval_proto.py
index b7f79ec..f40ba18 100755
--- a/benchmark/eval_proto.py
+++ b/benchmark/eval_proto.py
@@ -28,7 +28,7 @@ def div(a, b):
     if a == MIN_INT and b == -1:
         return MAX_INT
 
-    return a / b
+    return a // b
 
 def mod(a, b):
     if b == 0:
@@ -109,4 +109,4 @@ class Benchmark:
         response.value = evaluate_expression(request)
 
     def check(self, response, expected):
-        return response.value == expected
\ No newline at end of file
+        return response.value == expected
diff --git a/benchmark/eval_pycapnp.py b/benchmark/eval_pycapnp.py
index 913cb54..1af93d9 100755
--- a/benchmark/eval_pycapnp.py
+++ b/benchmark/eval_pycapnp.py
@@ -29,7 +29,7 @@ def div(a, b):
     if a == MIN_INT and b == -1:
         return MAX_INT
 
-    return a / b
+    return a // b
 
 def mod(a, b):
     if b == 0: