diff --git a/server/autoserv b/server/autoserv
index cc8619e..6fd9d31 100755
--- a/server/autoserv
+++ b/server/autoserv
@@ -141,6 +141,7 @@
     )
 
     namespace = {'machines': machines_list,
+                 'isolate_hash': parser.options.isolate,
                  'image': parser.options.test_source_build}
     script_locals = {}
     execfile(STAGE_SERVER_SIDE_PACKAGE_CONTROL_FILE, namespace, script_locals)
diff --git a/server/autoserv_parser.py b/server/autoserv_parser.py
index 5602b6a..2081c3d 100644
--- a/server/autoserv_parser.py
+++ b/server/autoserv_parser.py
@@ -174,6 +174,13 @@
                                  dest='no_use_packaging', default=False,
                                  help=('Disable install modes that use the '
                                        'packaging system.'))
+        self.parser.add_argument('--source_isolate', action='store',
+                                 type=str, default='',
+                                 dest='isolate',
+                                 help=('Hash for isolate containing build '
+                                       'contents needed for server-side '
+                                       'packaging. Takes precedence over '
+                                       'test_source_build, if present.'))
         self.parser.add_argument('--test_source_build', action='store',
                                  type=str, default='',
                                  dest='test_source_build',