diff --git a/lib/logger/log_device.rb b/lib/logger/log_device.rb
index 4876adf..5d90ef1 100644
--- a/lib/logger/log_device.rb
+++ b/lib/logger/log_device.rb
@@ -17,16 +17,7 @@ def initialize(log = nil, shift_age: nil, shift_size: nil, shift_period_suffix:
       @reraise_write_errors = reraise_write_errors
       mon_initialize
       set_dev(log)
-      if @filename
-        @shift_age = shift_age || 7
-        @shift_size = shift_size || 1048576
-        @shift_period_suffix = shift_period_suffix || '%Y%m%d'
-
-        unless @shift_age.is_a?(Integer)
-          base_time = @dev.respond_to?(:stat) ? @dev.stat.mtime : Time.now
-          @next_rotate_time = next_rotate_time(base_time, @shift_age)
-        end
-      end
+      set_shift(shift_age, shift_size, shift_period_suffix)
     end
 
     def write(message)
@@ -76,6 +67,7 @@ def reopen(log = nil)
             @filename = nil
           end
           set_dev(log)
+          set_shift
         end
       end
       self
@@ -99,6 +91,19 @@ def set_dev(log)
       end
     end
 
+    def set_shift(shift_age = @shift_age, shift_size = @shift_size, shift_period_suffix = @shift_period_suffix)
+      if @filename
+        @shift_age = shift_age || 7
+        @shift_size = shift_size || 1048576
+        @shift_period_suffix = shift_period_suffix || '%Y%m%d'
+
+        unless @shift_age.is_a?(Integer)
+          base_time = @dev.respond_to?(:stat) ? @dev.stat.mtime : Time.now
+          @next_rotate_time = next_rotate_time(base_time, @shift_age)
+        end
+      end
+    end
+
     def open_logfile(filename)
       begin
         File.open(filename, (File::WRONLY | File::APPEND))
diff --git a/test/logger/test_logdevice.rb b/test/logger/test_logdevice.rb
index 8f1c155..dd34714 100644
--- a/test/logger/test_logdevice.rb
+++ b/test/logger/test_logdevice.rb
@@ -5,6 +5,14 @@
 require 'tmpdir'
 
 class TestLogDevice < Test::Unit::TestCase
+  module LogDeviceAttributes
+    refine Logger::LogDevice do
+      attr_reader :shift_age, :shift_size, :shift_period_suffix, :binmode, :reraise_write_errors
+    end
+  end
+
+  using LogDeviceAttributes
+
   class LogExcnRaiser
     def write(*arg)
       raise 'disk is full'
@@ -140,6 +148,7 @@ def test_reopen_io_by_file
     begin
       assert_file.exist?(@filename)
       assert_equal(@filename, logdev.filename)
+      assert_equal(7, logdev.shift_age)
       assert_not_predicate(old_dev, :closed?)
     ensure
       logdev.close