diff --git a/activerecord/lib/active_record/associations/association_proxy.rb b/activerecord/lib/active_record/associations/association_proxy.rb
index acdcd14ec8281..b617147f674a9 100644
--- a/activerecord/lib/active_record/associations/association_proxy.rb
+++ b/activerecord/lib/active_record/associations/association_proxy.rb
@@ -240,7 +240,7 @@ def foreign_key_present
         # the kind of the class of the associated objects. Meant to be used as
         # a sanity check when you are about to assign an associated record.
         def raise_on_type_mismatch(record)
-          unless record.is_a?(@reflection.klass)
+          unless record.is_a?(@reflection.klass) || record.is_a?(@reflection.class_name.constantize)
             message = "#{@reflection.class_name}(##{@reflection.klass.object_id}) expected, got #{record.class}(##{record.class.object_id})"
             raise ActiveRecord::AssociationTypeMismatch, message
           end
diff --git a/activerecord/test/cases/reload_models_test.rb b/activerecord/test/cases/reload_models_test.rb
new file mode 100644
index 0000000000000..411b5f6afabcf
--- /dev/null
+++ b/activerecord/test/cases/reload_models_test.rb
@@ -0,0 +1,20 @@
+require "cases/helper"
+require 'models/owner'
+require 'models/pet'
+
+class ReloadModelsTest < ActiveRecord::TestCase
+  def test_has_one_with_reload
+    pet = Pet.find_by_name('parrot')
+    pet.owner = Owner.find_by_name('ashley')
+
+    # Reload the class Owner, simulating auto-reloading of model classes in a
+    # development environment. Note that meanwhile the class Pet is not
+    # reloaded, simulating a class that is present in a plugin.
+    Object.class_eval { remove_const :Owner }
+    Kernel.load(File.expand_path(File.join(File.dirname(__FILE__), "../models/owner.rb")))
+
+    pet = Pet.find_by_name('parrot')
+    pet.owner = Owner.find_by_name('ashley')
+    assert_equal pet.owner, Owner.find_by_name('ashley')
+  end
+end
\ No newline at end of file