diff --git a/actionpack/lib/action_controller/metal/params_wrapper.rb b/actionpack/lib/action_controller/metal/params_wrapper.rb
index 68881b8402676115eddab330f5cdc89787642fc3..44151c9f719722388224ddfd0e8e7c64c31f1c13 100644
--- a/actionpack/lib/action_controller/metal/params_wrapper.rb
+++ b/actionpack/lib/action_controller/metal/params_wrapper.rb
@@ -282,7 +282,7 @@ def _wrapper_enabled?
         return false unless request.has_content_type?
 
         ref = request.content_mime_type.ref
-        _wrapper_formats.include?(ref) && _wrapper_key && !request.request_parameters[_wrapper_key]
+        _wrapper_formats.include?(ref) && _wrapper_key && !request.request_parameters.key?(_wrapper_key)
       end
   end
 end
diff --git a/actionpack/test/controller/params_wrapper_test.rb b/actionpack/test/controller/params_wrapper_test.rb
index 2a41d57b26bdb15e6638c4d50aaf80afcc9b2236..4cbb28ef603ab031fa3af05cd2b6c2796a798589 100644
--- a/actionpack/test/controller/params_wrapper_test.rb
+++ b/actionpack/test/controller/params_wrapper_test.rb
@@ -170,6 +170,14 @@ def test_no_double_wrap_if_key_exists
     end
   end
 
+  def test_no_double_wrap_if_key_exists_and_value_is_nil
+    with_default_wrapper_options do
+      @request.env["CONTENT_TYPE"] = "application/json"
+      post :parse, params: { "user" => nil }
+      assert_parameters("user" => nil)
+    end
+  end
+
   def test_nested_params
     with_default_wrapper_options do
       @request.env["CONTENT_TYPE"] = "application/json"