diff --git a/python/google/protobuf/internal/decoder.py b/python/google/protobuf/internal/decoder.py
index ff3e6d306..52b64915c 100755
--- a/python/google/protobuf/internal/decoder.py
+++ b/python/google/protobuf/internal/decoder.py
@@ -181,7 +181,7 @@ def ReadTag(buffer, pos):
   while six.indexbytes(buffer, pos) & 0x80:
     pos += 1
   pos += 1
-  return (buffer[start:pos], pos)
+  return (six.binary_type(buffer[start:pos]), pos)
 
 
 # --------------------------------------------------------------------
diff --git a/python/google/protobuf/internal/encoder.py b/python/google/protobuf/internal/encoder.py
index 8c6a11892..40c62d670 100755
--- a/python/google/protobuf/internal/encoder.py
+++ b/python/google/protobuf/internal/encoder.py
@@ -418,7 +418,7 @@ def _VarintBytes(value):
 def TagBytes(field_number, wire_type):
   """Encode the given tag and return the bytes.  Only called at startup."""
 
-  return _VarintBytes(wire_format.PackTag(field_number, wire_type))
+  return six.binary_type( _VarintBytes(wire_format.PackTag(field_number, wire_type)) )
 
 # --------------------------------------------------------------------
 # As with sizers (see above), we have a number of common encoder