1 files changed, 6 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/core_ext/object/json.rb b/activesupport/lib/active_support/core_ext/object/json.rb
index 0a3b875f24..f7c623fe13 100644
--- a/activesupport/lib/active_support/core_ext/object/json.rb
+++ b/activesupport/lib/active_support/core_ext/object/json.rb
@@ -135,6 +135,12 @@ module Enumerable
   end
 end
 
+class IO
+  def as_json(options = nil) #:nodoc:
+    to_s
+  end
+end
+
 class Range
   def as_json(options = nil) #:nodoc:
     to_s