diff --git a/lib/logger/log_device.rb b/lib/logger/log_device.rb
index 45545fa..dbbc0d9 100644
--- a/lib/logger/log_device.rb
+++ b/lib/logger/log_device.rb
@@ -184,6 +184,7 @@ def lock_shift_log
             @dev = open_logfile(@filename)
           end
         end
+        true
       rescue Errno::ENOENT
         # @filename file would not exist right after #rename and before #create_logfile
         if retry_limit <= 0
@@ -205,10 +206,7 @@ def shift_log_age
           File.rename("#{@filename}.#{i}", "#{@filename}.#{i+1}")
         end
       end
-      @dev.close rescue nil
-      File.rename("#{@filename}", "#{@filename}.0")
-      @dev = create_logfile(@filename)
-      return true
+      shift_log_file("#{@filename}.0")
     end
 
     def shift_log_period(period_end)
@@ -224,8 +222,12 @@ def shift_log_period(period_end)
           break unless FileTest.exist?(age_file)
         end
       end
+      shift_log_file(age_file)
+    end
+
+    def shift_log_file(shifted)
       @dev.close rescue nil
-      File.rename("#{@filename}", age_file)
+      File.rename(@filename, shifted)
       @dev = create_logfile(@filename)
       return true
     end
diff --git a/test/logger/test_logdevice.rb b/test/logger/test_logdevice.rb
index 05d3f63..a65ceaf 100644
--- a/test/logger/test_logdevice.rb
+++ b/test/logger/test_logdevice.rb
@@ -842,8 +842,6 @@ class << Time
     end
   end
 
-  env_tz_works = /linux|darwin|freebsd/ =~ RUBY_PLATFORM # borrow from test/ruby/test_time_tz.rb
-
   def test_shifting_weekly_exist_file
     Dir.mktmpdir do |tmpdir|
       assert_in_out_err([{"TZ"=>"UTC"}, *%W"-I#{@top_dir} -rlogger -C#{tmpdir} -"], "#{<<-"begin;"}\n#{<<-'end;'}")