3 files changed, 17 insertions, 5 deletions
diff --git a/activemodel/CHANGELOG.md b/activemodel/CHANGELOG.md
index 9cebb680fc..77386e5e41 100644
--- a/activemodel/CHANGELOG.md
+++ b/activemodel/CHANGELOG.md
@@ -1,3 +1,14 @@
+*   Assigning an unknown attribute key to an `ActiveModel` instance during initialization
+    will now raise `ActiveModel::AttributeAssignment::UnknownAttributeError` instead of
+    `NoMethodError`
+
+    ```ruby
+    User.new(foo: 'some value')
+    # => ActiveModel::AttributeAssignment::UnknownAttributeError: unknown attribute 'foo' for User.
+    ```
+
+    *Eugene Gilburg*
+
 *   Extracted `ActiveRecord::AttributeAssignment` to `ActiveModel::AttributeAssignment`
     allowing to use it for any object as an includable module
 
diff --git a/activemodel/lib/active_model/model.rb b/activemodel/lib/active_model/model.rb
index d51d6ddcc9..dac8d549a7 100644
--- a/activemodel/lib/active_model/model.rb
+++ b/activemodel/lib/active_model/model.rb
@@ -57,6 +57,7 @@ module ActiveModel
   # (see below).
   module Model
     extend ActiveSupport::Concern
+    include ActiveModel::AttributeAssignment
     include ActiveModel::Validations
     include ActiveModel::Conversion
 
@@ -75,10 +76,8 @@ module ActiveModel
     #   person = Person.new(name: 'bob', age: '18')
     #   person.name # => "bob"
     #   person.age  # => "18"
-    def initialize(params={})
-      params.each do |attr, value|
-        self.public_send("#{attr}=", value)
-      end if params
+    def initialize(attributes={})
+      assign_attributes(attributes) if attributes
 
       super()
     end
diff --git a/activemodel/test/cases/model_test.rb b/activemodel/test/cases/model_test.rb
index ee0fa26546..9a8d873ec9 100644
--- a/activemodel/test/cases/model_test.rb
+++ b/activemodel/test/cases/model_test.rb
@@ -70,6 +70,8 @@ class ModelTest < ActiveModel::TestCase
   end
 
   def test_mixin_initializer_when_args_dont_exist
-    assert_raises(NoMethodError) { SimpleModel.new(hello: 'world') }
+    assert_raises(ActiveModel::AttributeAssignment::UnknownAttributeError) do
+      SimpleModel.new(hello: 'world')
+    end
   end
 end