diff --git a/activerecord/lib/active_record/attribute_methods/before_type_cast.rb b/activerecord/lib/active_record/attribute_methods/before_type_cast.rb
index bde11d0494..d4f529acbf 100644
--- a/activerecord/lib/active_record/attribute_methods/before_type_cast.rb
+++ b/activerecord/lib/active_record/attribute_methods/before_type_cast.rb
@@ -20,11 +20,7 @@ module ActiveRecord
 
       # Handle *_before_type_cast for method_missing.
       def attribute_before_type_cast(attribute_name)
-        if attribute_name == 'id'
-          read_attribute_before_type_cast(self.class.primary_key)
-        else
-          read_attribute_before_type_cast(attribute_name)
-        end
+        read_attribute_before_type_cast(attribute_name)
       end
     end
   end
diff --git a/activerecord/lib/active_record/attribute_methods/primary_key.rb b/activerecord/lib/active_record/attribute_methods/primary_key.rb
index 2e1a2dc3ef..8e0b3e1402 100644
--- a/activerecord/lib/active_record/attribute_methods/primary_key.rb
+++ b/activerecord/lib/active_record/attribute_methods/primary_key.rb
@@ -1,3 +1,5 @@
+require 'set'
+
 module ActiveRecord
   module AttributeMethods
     module PrimaryKey
@@ -24,6 +26,11 @@ module ActiveRecord
         query_attribute(self.class.primary_key)
       end
 
+      # Returns the primary key value before type cast
+      def id_before_type_cast
+        read_attribute_before_type_cast(self.class.primary_key)
+      end
+
       protected
 
       def attribute_method?(attr_name)
@@ -45,8 +52,10 @@ module ActiveRecord
           end
         end
 
+        ID_ATTRIBUTE_METHODS = %w(id id= id? id_before_type_cast).to_set
+
         def dangerous_attribute_method?(method_name)
-          super && !['id', 'id=', 'id?'].include?(method_name)
+          super && !ID_ATTRIBUTE_METHODS.include?(method_name)
         end
 
         # Defines the primary key field -- can be overridden in subclasses. Overwriting will negate any effect of the
diff --git a/activerecord/test/cases/attribute_methods_test.rb b/activerecord/test/cases/attribute_methods_test.rb
index 3ac2a76b96..4078b7eb0b 100644
--- a/activerecord/test/cases/attribute_methods_test.rb
+++ b/activerecord/test/cases/attribute_methods_test.rb
@@ -121,6 +121,14 @@ class AttributeMethodsTest < ActiveRecord::TestCase
     assert keyboard.respond_to?('id')
   end
 
+  def test_id_before_type_cast_with_custom_primary_key
+    keyboard = Keyboard.create
+    keyboard.key_number = '10'
+    assert_equal '10', keyboard.id_before_type_cast
+    assert_equal nil, keyboard.read_attribute_before_type_cast('id')
+    assert_equal '10', keyboard.read_attribute_before_type_cast('key_number')
+  end
+
   # Syck calls respond_to? before actually calling initialize
   def test_respond_to_with_allocated_object
     topic = Topic.allocate