diff --git a/scrapyd/environ.py b/scrapyd/environ.py
index bf511a4cf..a41e6abb9 100644
--- a/scrapyd/environ.py
+++ b/scrapyd/environ.py
@@ -21,6 +21,7 @@ class Environment(object):
     def get_environment(self, message, slot, eggpath):
         project = message['_project']
         env = self.initenv.copy()
+        env['SCRAPY_SLOT'] = str(slot)
         env['SCRAPY_PROJECT'] = project
         if eggpath:
             env['SCRAPY_EGGFILE'] = eggpath
diff --git a/scrapyd/tests/test_environ.py b/scrapyd/tests/test_environ.py
index b7c3d97ef..09cac50ae 100644
--- a/scrapyd/tests/test_environ.py
+++ b/scrapyd/tests/test_environ.py
@@ -26,6 +26,7 @@ class EggStorageTest(unittest.TestCase):
         slot = 3
         env = self.environ.get_environment(msg, slot, '/path/to/file.egg')
         self.assertEqual(env['SCRAPY_PROJECT'], 'mybot')
+        self.assertEqual(env['SCRAPY_SLOT'], '3')
         self.assert_(env['SCRAPY_SQLITE_DB'].endswith('mybot.db'))
         self.assert_(env['SCRAPY_LOG_FILE'].endswith('/mybot/myspider/ID.log'))
         self.assert_(env['SCRAPY_EGGFILE'].endswith('/path/to/file.egg'))
@@ -36,6 +37,7 @@ class EggStorageTest(unittest.TestCase):
         slot = 3
         env = self.environ.get_environment(msg, slot, None)
         self.assertEqual(env['SCRAPY_PROJECT'], 'newbot')
+        self.assertEqual(env['SCRAPY_SLOT'], '3')
         self.assert_(env['SCRAPY_SQLITE_DB'].endswith('newbot.db'))
         self.assert_(env['SCRAPY_LOG_FILE'].endswith('/newbot/myspider/ID.log'))
         self.assertEqual(env['SCRAPY_SETTINGS_MODULE'], 'newbot.settings')