1 files changed, 8 insertions, 0 deletions
diff --git a/actionpack/test/controller/parameters/accessors_test.rb b/actionpack/test/controller/parameters/accessors_test.rb
index 07a897a103..674b2c6266 100644
--- a/actionpack/test/controller/parameters/accessors_test.rb
+++ b/actionpack/test/controller/parameters/accessors_test.rb
@@ -284,4 +284,12 @@ class ParametersAccessorsTest < ActiveSupport::TestCase
       value.is_a?(ActionController::Parameters)
     end
   end
+
+  test "mutating #dig return value mutates underlying parameters" do
+    @params.dig(:person, :name)[:first] = "Bill"
+    assert_equal "Bill", @params.dig(:person, :name, :first)
+
+    @params.dig(:person, :addresses)[0] = { city: "Boston", state: "Massachusetts" }
+    assert_equal "Boston", @params.dig(:person, :addresses, 0, :city)
+  end
 end