1 files changed, 6 insertions, 0 deletions
diff --git a/python/google/protobuf/internal/decoder.py b/python/google/protobuf/internal/decoder.py
index 55f746f5..cb6f5729 100755
--- a/python/google/protobuf/internal/decoder.py
+++ b/python/google/protobuf/internal/decoder.py
@@ -576,6 +576,7 @@ def MessageSetItemDecoder(extensions_by_number):
   local_SkipField = SkipField
 
   def DecodeItem(buffer, pos, end, message, field_dict):
+    message_set_item_start = pos
     type_id = -1
     message_start = -1
     message_end = -1
@@ -614,6 +615,11 @@ def MessageSetItemDecoder(extensions_by_number):
         # The only reason _InternalParse would return early is if it encountered
         # an end-group tag.
         raise _DecodeError('Unexpected end-group tag.')
+    else:
+      if not message._unknown_fields:
+        message._unknown_fields = []
+      message._unknown_fields.append((MESSAGE_SET_ITEM_TAG,
+                                      buffer[message_set_item_start:pos]))
 
     return pos