diff --git a/lib/fluent/plugin/out_s3.rb b/lib/fluent/plugin/out_s3.rb
index 9149a0b..2c4e06a 100644
--- a/lib/fluent/plugin/out_s3.rb
+++ b/lib/fluent/plugin/out_s3.rb
@@ -632,16 +632,24 @@ def compress(chunk, tmp)
     end
 
     class ZstdCompressor < Compressor
+      def initialize(level = 3)
+        @level = level
+      end
+    
       def ext
         'zst'.freeze
       end
-
+    
       def content_type
         'application/x-zst'.freeze
       end
-
+    
       def compress(chunk, tmp)
-        compressed_data = Zstd.compress(chunk.read, level: @level)
+        uncompressed_data = ''
+        chunk.open do |io|
+          uncompressed_data = io.read
+        end
+        compressed_data = Zstd.compress(uncompressed_data, level: @level)
         tmp.write(compressed_data)
       rescue => e
         log.warn "zstd compression failed: #{e.message}"