diff --git a/lib/yunq/serialize.cpp b/lib/yunq/serialize.cpp
index 7b7852d..9d58ac8 100644
--- a/lib/yunq/serialize.cpp
+++ b/lib/yunq/serialize.cpp
@@ -3,7 +3,7 @@
 namespace yunq {
 namespace {
 
-const uint64_t kIdentByte = 0x33441122;
+const uint32_t kIdentByte = 0x33441122;
 
 }  // namespace
 
diff --git a/lib/yunq/serialize.h b/lib/yunq/serialize.h
index b0c84c3..170917f 100644
--- a/lib/yunq/serialize.h
+++ b/lib/yunq/serialize.h
@@ -100,7 +100,7 @@ template <typename T>
 void Serializer::WriteRepeatedMessage(uint64_t field_index,
                                       const glcr::Vector<T>& value) {
   uint64_t next_offset = next_extension_;
-  uint64_t length = 0;
+  uint64_t length = value.size();
 
   for (T& message : value) {
     uint64_t msg_length = 0;
@@ -110,7 +110,6 @@ void Serializer::WriteRepeatedMessage(uint64_t field_index,
     } else {
       msg_length = message.SerializeToBytes(buffer_, offset_ + next_offset);
     }
-    length += msg_length;
     next_offset += msg_length;
   }
 
@@ -119,7 +118,7 @@ void Serializer::WriteRepeatedMessage(uint64_t field_index,
       .length = (uint32_t)length,
   };
 
-  next_extension_ += length;
+  next_extension_ = next_offset;
 
   buffer_.WriteAt<ExtensionPointer>(field_offset(field_index), ptr);
 }