diff --git a/lib/fluent/plugin/buffer.rb b/lib/fluent/plugin/buffer.rb
index b34f6c824f..cda7926fab 100644
--- a/lib/fluent/plugin/buffer.rb
+++ b/lib/fluent/plugin/buffer.rb
@@ -748,23 +748,23 @@ def write_step_by_step(metadata, data, format, splits_count, &block)
         modified_chunks = []
         modified_metadata = metadata
         get_next_chunk = ->(){
-          c = if staged_chunk_used
-                # Staging new chunk here is bad idea:
-                # Recovering whole state including newly staged chunks is much harder than current implementation.
-                modified_metadata = modified_metadata.dup_next
-                generate_chunk(modified_metadata)
-              else
-                synchronize { @stage[modified_metadata] ||= generate_chunk(modified_metadata).staged! }
-              end
-          modified_chunks << {chunk: c, adding_bytesize: 0, errors: []}
-          return c, modified_chunks.last[:errors]
+          if staged_chunk_used
+            # Staging new chunk here is bad idea:
+            # Recovering whole state including newly staged chunks is much harder than current implementation.
+            modified_metadata = modified_metadata.dup_next
+            generate_chunk(modified_metadata)
+          else
+            synchronize { @stage[modified_metadata] ||= generate_chunk(modified_metadata).staged! }
+          end
         }
 
         writing_splits_index = 0
         enqueue_chunk_before_retry = false
 
         while writing_splits_index < splits.size
-          chunk, errors = get_next_chunk.call
+          chunk = get_next_chunk.call
+          errors = []
+          modified_chunks << {chunk: chunk, adding_bytesize: 0, errors: errors}
           chunk.synchronize do
             raise ShouldRetry unless chunk.writable?
             staged_chunk_used = true if chunk.staged?