diff --git a/scrapy/spider/models.py b/scrapy/spider/models.py
index 094cd5077..615e920a6 100644
--- a/scrapy/spider/models.py
+++ b/scrapy/spider/models.py
@@ -34,13 +34,14 @@ class BaseSpider(object_ref):
         self.__dict__.update(kwargs)
         # XXX: SEP-12 backward compatibility (remove for 0.10)
         if hasattr(self, 'domain_name'):
-            warnings.warn("Spider.domain_name attribute is deprecated, use Spider.name instead", \
+            warnings.warn("Spider.domain_name attribute is deprecated, use Spider.name instead and Spider.allowed_domains", \
                 DeprecationWarning, stacklevel=4)
             self.name = self.domain_name
-        if hasattr(self, 'extra_domain_names'):
-            warnings.warn("Spider.extra_domain_names attribute is deprecated - user Spider.allowed_domains instead", \
-                DeprecationWarning, stacklevel=4)
-            self.allowed_domains = [self.name] + list(self.extra_domain_names)
+            self.allowed_domains = [self.name]
+            if hasattr(self, 'extra_domain_names'):
+                warnings.warn("Spider.extra_domain_names attribute is deprecated - user Spider.allowed_domains instead", \
+                    DeprecationWarning, stacklevel=4)
+                self.allowed_domains += list(self.extra_domain_names)
 
         if name is not None:
             self.name = name
@@ -50,13 +51,13 @@ class BaseSpider(object_ref):
             self.start_urls = []
         if not self.allowed_domains:
             self.allowed_domains = []
-        if not getattr(self, 'domain_name', None):
-            self.domain_name = self.name
-        if not getattr(self, 'extra_domain_names', None):
-            self.extra_domain_names = self.allowed_domains
         if not self.name:
             self.name = 'default'
 
+        # XXX: SEP-12 forward compatibility (remove for 0.10)
+        self.domain_name = self.name
+        self.extra_domain_names = self.allowed_domains
+
     def log(self, message, level=log.DEBUG):
         """Log the given messages at the given log level. Always use this
         method to send log messages from your spider
diff --git a/scrapy/tests/test_spider.py b/scrapy/tests/test_spider.py
index 7d93db5b5..9a618e720 100644
--- a/scrapy/tests/test_spider.py
+++ b/scrapy/tests/test_spider.py
@@ -11,6 +11,7 @@ from scrapy.contrib.spiders.crawl import CrawlSpider
 from scrapy.contrib.spiders.feed import XMLFeedSpider, CSVFeedSpider
 from scrapy.contrib.dupefilter import RequestFingerprintDupeFilter, NullDupeFilter
 
+
 class BaseSpiderTest(unittest.TestCase):
 
     spider_class = BaseSpider
@@ -20,6 +21,12 @@ class BaseSpiderTest(unittest.TestCase):
         domain_name = 'example.com'
         extra_domain_names = ('example.org', 'example.net')
 
+
+    class OldSpiderWithoutExtradomains(spider_class):
+
+        domain_name = 'example.com'
+
+
     class NewSpider(spider_class):
 
         name = 'example.com'
@@ -48,6 +55,10 @@ class BaseSpiderTest(unittest.TestCase):
         self.assert_('example.org' in spider.allowed_domains, spider.allowed_domains)
         self.assert_('example.net' in spider.allowed_domains, spider.allowed_domains)
 
+        spider = self.OldSpiderWithoutExtradomains()
+        self.assertEqual(spider.name, 'example.com')
+        self.assert_('example.com' in spider.allowed_domains, spider.allowed_domains)
+
         spider = self.NewSpider()
         self.assertEqual(spider.domain_name, 'example.com')
         self.assert_('example.org' in spider.extra_domain_names, spider.extra_domain_names)