diff --git a/lib/fluent/plugin/in_tail.rb b/lib/fluent/plugin/in_tail.rb
index b2fa734a1f..8bbac620bd 100644
--- a/lib/fluent/plugin/in_tail.rb
+++ b/lib/fluent/plugin/in_tail.rb
@@ -732,7 +732,7 @@ def handle_notify
               if !io.nil? && @lines.empty?
                 begin
                   while true
-                    @fifo << io.readpartial(2048, @iobuf)
+                    @fifo << io.readpartial(8192, @iobuf)
                     while (line = @fifo.next_line)
                       @lines << line
                     end
diff --git a/test/plugin/test_in_tail.rb b/test/plugin/test_in_tail.rb
index f1ddc4606d..c37bc2092e 100644
--- a/test/plugin/test_in_tail.rb
+++ b/test/plugin/test_in_tail.rb
@@ -196,7 +196,7 @@ def test_emit_with_read_lines_limit(data)
         config = CONFIG_READ_FROM_HEAD + config_element("", "", { "read_lines_limit" => limit }) + PARSE_SINGLE_LINE_CONFIG
       end
       d = create_driver(config)
-      msg = 'test' * 500 # in_tail reads 2048 bytes at once.
+      msg = 'test' * 2000 # in_tail reads 8192 bytes at once.
 
       d.run(expect_emits: 1) do
         File.open("#{TMP_DIR}/tail.txt", "ab") {|f|