diff --git a/activesupport/lib/active_support/buffered_logger.rb b/activesupport/lib/active_support/buffered_logger.rb
index fad47b0e9b7d5256e7a31ea5fd93d10918d1d025..08e71e5b8cccac7f71f3be681614cedede002d97 100644
--- a/activesupport/lib/active_support/buffered_logger.rb
+++ b/activesupport/lib/active_support/buffered_logger.rb
@@ -91,7 +91,7 @@ def auto_flushing=(period)
     end
 
     def flush
-      @log.write(@buffer.slice!(0..-1)) unless @buffer.empty?
+      @log.write(@buffer.slice!(0..-1).to_s) unless @buffer.empty?
     end
 
     def close