diff --git a/activesupport/test/json/encoding_test.rb b/activesupport/test/json/encoding_test.rb
index 95bdc4283a7afcaa8e01729f1c2ee6c54b7eb60b..7d6ab585efd22c2a8d2f4fcc8862525c5ff9d247 100644
--- a/activesupport/test/json/encoding_test.rb
+++ b/activesupport/test/json/encoding_test.rb
@@ -444,7 +444,7 @@ def test_to_json_works_when_as_json_returns_infinite_number
 
   class NaNNumber
     def as_json(options = nil)
-      { "number" => Float::INFINITY }
+      { "number" => Float:NAN }
     end
   end