3 files changed, 5 insertions, 8 deletions
diff --git a/activesupport/lib/active_support/json/backends/jsongem.rb b/activesupport/lib/active_support/json/backends/jsongem.rb
index 649e6301d1..c6c17a3c4e 100644
--- a/activesupport/lib/active_support/json/backends/jsongem.rb
+++ b/activesupport/lib/active_support/json/backends/jsongem.rb
@@ -2,10 +2,9 @@ require 'json' unless defined?(JSON)
 
 module ActiveSupport
   module JSON
-    ParseError = ::JSON::ParserError unless const_defined?(:ParseError)
-
     module Backends
       module JSONGem
+        ParseError = ::JSON::ParserError
         extend self
 
         # Parses a JSON string or IO and convert it into an object
@@ -38,4 +37,4 @@ module ActiveSupport
       end
     end
   end
-end
-\ No newline at end of file
+end
diff --git a/activesupport/lib/active_support/json/backends/yaml.rb b/activesupport/lib/active_support/json/backends/yaml.rb
index 59d2c37e40..215b3d6f90 100644
--- a/activesupport/lib/active_support/json/backends/yaml.rb
+++ b/activesupport/lib/active_support/json/backends/yaml.rb
@@ -2,13 +2,9 @@ require 'active_support/core_ext/string/starts_ends_with'
 
 module ActiveSupport
   module JSON
-    unless const_defined?(:ParseError)
-      class ParseError < StandardError
-      end
-    end
-
     module Backends
       module Yaml
+        ParseError = ::StandardError
         extend self
 
         # Parses a JSON string or IO and converts it into an object
diff --git a/activesupport/lib/active_support/json/decoding.rb b/activesupport/lib/active_support/json/decoding.rb
index 356b6cebeb..a5908365af 100644
--- a/activesupport/lib/active_support/json/decoding.rb
+++ b/activesupport/lib/active_support/json/decoding.rb
@@ -7,6 +7,7 @@ module ActiveSupport
 
   module JSON
     class << self
+      attr_reader :parse_error
       delegate :decode, :to => :backend
 
       def backend
@@ -21,6 +22,7 @@ module ActiveSupport
           require "active_support/json/backends/#{name.to_s.downcase}.rb"
           @backend = ActiveSupport::JSON::Backends::const_get(name)
         end
+        @parse_error = @backend::ParseError
       end
 
       def with_backend(name)