diff --git a/activemodel/CHANGELOG.md b/activemodel/CHANGELOG.md
index e20ebde8b1..9cebb680fc 100644
--- a/activemodel/CHANGELOG.md
+++ b/activemodel/CHANGELOG.md
@@ -6,7 +6,7 @@
       include ActiveModel::AttributeAssignment
       attr_accessor :name, :status
     end
-    
+
     cat = Cat.new
     cat.assign_attributes(name: "Gorby", status: "yawning")
     cat.name # => 'Gorby'
diff --git a/activemodel/lib/active_model/attribute_assignment.rb b/activemodel/lib/active_model/attribute_assignment.rb
index 36ddbad826..356421476c 100644
--- a/activemodel/lib/active_model/attribute_assignment.rb
+++ b/activemodel/lib/active_model/attribute_assignment.rb
@@ -34,6 +34,7 @@ module ActiveModel
     end
 
     private
+
     def _assign_attributes(attributes)
       attributes.each do |k, v|
         _assign_attribute(k, v)
@@ -41,10 +42,8 @@ module ActiveModel
     end
 
     def _assign_attribute(k, v)
-      public_send("#{k}=", v)
-    rescue NoMethodError
       if respond_to?("#{k}=")
-        raise
+        public_send("#{k}=", v)
       else
         raise UnknownAttributeError.new(self, k)
       end
diff --git a/activemodel/test/cases/attribute_assignment_test.rb b/activemodel/test/cases/attribute_assignment_test.rb
index 5c1be6a456..402caf21f7 100644
--- a/activemodel/test/cases/attribute_assignment_test.rb
+++ b/activemodel/test/cases/attribute_assignment_test.rb
@@ -1,8 +1,7 @@
-require 'cases/helper'
-require 'active_support/hash_with_indifferent_access' 
+require "cases/helper"
+require "active_support/hash_with_indifferent_access"
 
 class AttributeAssignmentTest < ActiveModel::TestCase
-
   class Model
     include ActiveModel::AttributeAssignment
 
@@ -13,13 +12,15 @@ class AttributeAssignmentTest < ActiveModel::TestCase
     end
 
     def broken_attribute=(value)
-      non_existing_method(value)
+      raise ErrorFromAttributeWriter
     end
 
-    private
-    def metadata=(data)
-      @metadata = data
-    end
+    protected
+
+    attr_writer :metadata
+  end
+
+  class ErrorFromAttributeWriter < StandardError
   end
 
   class ProtectedParams < ActiveSupport::HashWithIndifferentAccess
@@ -41,14 +42,14 @@ class AttributeAssignmentTest < ActiveModel::TestCase
   test "simple assignment" do
     model = Model.new
 
-    model.assign_attributes(name: 'hello', description: 'world')
-    assert_equal 'hello', model.name
-    assert_equal 'world', model.description
+    model.assign_attributes(name: "hello", description: "world")
+    assert_equal "hello", model.name
+    assert_equal "world", model.description
   end
 
   test "assign non-existing attribute" do
     model = Model.new
-    error = assert_raises ActiveModel::AttributeAssignment::UnknownAttributeError do
+    error = assert_raises(ActiveModel::AttributeAssignment::UnknownAttributeError) do
       model.assign_attributes(hz: 1)
     end
 
@@ -58,49 +59,49 @@ class AttributeAssignmentTest < ActiveModel::TestCase
 
   test "assign private attribute" do
     model = Model.new
-    assert_raises ActiveModel::AttributeAssignment::UnknownAttributeError do
+    assert_raises(ActiveModel::AttributeAssignment::UnknownAttributeError) do
       model.assign_attributes(metadata: { a: 1 })
     end
   end
 
-  test "raises NoMethodError if raised in attribute writer" do
-    assert_raises NoMethodError do
+  test "does not swallow errors raised in an attribute writer" do
+    assert_raises(ErrorFromAttributeWriter) do
       Model.new(broken_attribute: 1)
     end
   end
 
-  test "raises ArgumentError if non-hash object passed" do
-    assert_raises ArgumentError do
+  test "an ArgumentError is raised if a non-hash-like obejct is passed" do
+    assert_raises(ArgumentError) do
       Model.new(1)
     end
   end
 
-  test 'forbidden attributes cannot be used for mass assignment' do
-    params = ProtectedParams.new(name: 'Guille', description: 'm')
+  test "forbidden attributes cannot be used for mass assignment" do
+    params = ProtectedParams.new(name: "Guille", description: "m")
+
     assert_raises(ActiveModel::ForbiddenAttributesError) do
       Model.new(params)
     end
   end
 
-  test 'permitted attributes can be used for mass assignment' do
-    params = ProtectedParams.new(name: 'Guille', description: 'desc')
+  test "permitted attributes can be used for mass assignment" do
+    params = ProtectedParams.new(name: "Guille", description: "desc")
     params.permit!
     model = Model.new(params)
 
-    assert_equal 'Guille', model.name
-    assert_equal 'desc', model.description
+    assert_equal "Guille", model.name
+    assert_equal "desc", model.description
   end
 
-  test 'regular hash should still be used for mass assignment' do
-    model = Model.new(name: 'Guille', description: 'm')
+  test "regular hash should still be used for mass assignment" do
+    model = Model.new(name: "Guille", description: "m")
 
-    assert_equal 'Guille', model.name
-    assert_equal 'm', model.description
+    assert_equal "Guille", model.name
+    assert_equal "m", model.description
   end
 
-  test 'blank attributes should not raise' do
+  test "assigning no attributes should not raise, even if the hash is un-permitted" do
     model = Model.new
     assert_nil model.assign_attributes(ProtectedParams.new({}))
   end
-
 end
diff --git a/activerecord/lib/active_record/attribute_assignment.rb b/activerecord/lib/active_record/attribute_assignment.rb
index e283db0386..e368fdfff9 100644
--- a/activerecord/lib/active_record/attribute_assignment.rb
+++ b/activerecord/lib/active_record/attribute_assignment.rb
@@ -22,22 +22,10 @@ module ActiveRecord
       assign_multiparameter_attributes(multi_parameter_attributes) unless multi_parameter_attributes.empty?
     end
 
-    # Allows you to set all the attributes by passing in a hash of attributes with
-    # keys matching the attribute names (which again matches the column names).
-    #
-    # If the passed hash responds to <tt>permitted?</tt> method and the return value
-    # of this method is +false+ an <tt>ActiveModel::ForbiddenAttributesError</tt>
-    # exception is raised.
-    #
-    #   cat = Cat.new(name: "Gorby", status: "yawning")
-    #   cat.attributes # =>  { "name" => "Gorby", "status" => "yawning", "created_at" => nil, "updated_at" => nil}
-    #   cat.assign_attributes(status: "sleeping")
-    #   cat.attributes # =>  { "name" => "Gorby", "status" => "sleeping", "created_at" => nil, "updated_at" => nil }
-    #
-    # New attributes will be persisted in the database when the object is saved.
-    #
-    # Aliased to <tt>assign_attributes</tt>.
-    alias attributes= assign_attributes
+    # Alias for `assign_attributes`. See +ActiveModel::AttributeAssignment+
+    def attributes=(attributes)
+      assign_attributes(attributes)
+    end
 
     private