diff --git a/kafka/coordinator/base.py b/kafka/coordinator/base.py
index 5658e31cc..af8d12143 100644
--- a/kafka/coordinator/base.py
+++ b/kafka/coordinator/base.py
@@ -540,10 +540,6 @@ def _send_join_group_request(self):
 
         # send a join group request to the coordinator
         log.info("(Re-)joining group %s", self.group_id)
-        member_metadata = [
-            (protocol, metadata if isinstance(metadata, bytes) else metadata.encode())
-            for protocol, metadata in self.group_protocols()
-        ]
         version = self._client.api_version(JoinGroupRequest, max_version=5)
         if version == 0:
             request = JoinGroupRequest[version](
@@ -551,7 +547,7 @@ def _send_join_group_request(self):
                 self.config['session_timeout_ms'],
                 self._generation.member_id,
                 self.protocol_type(),
-                member_metadata)
+                self.group_protocols())
         elif version <= 4:
             request = JoinGroupRequest[version](
                 self.group_id,
@@ -559,7 +555,7 @@ def _send_join_group_request(self):
                 self.config['max_poll_interval_ms'],
                 self._generation.member_id,
                 self.protocol_type(),
-                member_metadata)
+                self.group_protocols())
         else:
             request = JoinGroupRequest[version](
                 self.group_id,
@@ -568,7 +564,7 @@ def _send_join_group_request(self):
                 self._generation.member_id,
                 self.group_instance_id,
                 self.protocol_type(),
-                member_metadata)
+                self.group_protocols())
 
         # create the request for the coordinator
         log.debug("Sending JoinGroup (%s) to coordinator %s", request, self.coordinator_id)
@@ -706,10 +702,6 @@ def _on_join_leader(self, response):
             group_assignment = self._perform_assignment(response.leader_id,
                                                         response.group_protocol,
                                                         members)
-            for member_id, assignment in group_assignment.items():
-                if not isinstance(assignment, bytes):
-                    group_assignment[member_id] = assignment.encode()
-
         except Exception as e:
             return Future().failure(e)
 
diff --git a/kafka/protocol/types.py b/kafka/protocol/types.py
index 28369f29e..574b0f327 100644
--- a/kafka/protocol/types.py
+++ b/kafka/protocol/types.py
@@ -141,8 +141,9 @@ class Bytes(AbstractType):
     def encode(cls, value):
         if value is None:
             return Int32.encode(-1)
-        else:
-            return Int32.encode(len(value)) + value
+        elif not isinstance(value, bytes):
+            value = value.encode()
+        return Int32.encode(len(value)) + value
 
     @classmethod
     def decode(cls, data):
diff --git a/test/protocol/test_schema.py b/test/protocol/test_schema.py
index 4ad8d0d2f..85850f43b 100644
--- a/test/protocol/test_schema.py
+++ b/test/protocol/test_schema.py
@@ -3,7 +3,7 @@
 import pytest
 
 from kafka.protocol.struct import Struct
-from kafka.protocol.types import Schema, Int32, String, TaggedFields
+from kafka.protocol.types import Schema, Int32, String, TaggedFields, Bytes
 
 
 def test_schema_type():
@@ -52,3 +52,12 @@ def test_struct(args, kwargs):
     data = struct(*args, **kwargs)
     assert data.encode() == encoded
     assert struct.decode(encoded) == data
+
+
+def test_bytes_struct():
+    schema = Schema(('f1', Int32), ('f2', String()))
+    struct = type('TestStruct', (Struct,), {'SCHEMA': schema})
+    data = struct(f1=123, f2="bar")
+    bytes_encoded = Bytes.encode(data)
+    assert bytes_encoded[4:] == data.encode()
+    assert bytes_encoded[:4] == Int32.encode(len(data.encode()))