1 files changed, 1 insertions, 1 deletions
diff --git a/lib/logger.rb b/lib/logger.rb
index 04a106b448..e8e163ca93 100644
--- a/lib/logger.rb
+++ b/lib/logger.rb
@@ -322,7 +322,7 @@ private
     #
     def initialize(log = nil, opt = {})
       @dev = @filename = @shift_age = @shift_size = nil
-      if log.is_a?(IO)
+      if log.respond_to?(:write) and log.respond_to?(:close)
 	@dev = log
       elsif log.is_a?(String)
 	@dev = open_logfile(log)