allow only enforce login base prefix on new slices
diff --git a/planetstack/core/models/slice.py b/planetstack/core/models/slice.py
index 12c278b..7915d42 100644
--- a/planetstack/core/models/slice.py
+++ b/planetstack/core/models/slice.py
@@ -42,7 +42,8 @@
     def save(self, *args, **kwds):
         
         site = Site.objects.get(id=self.site.id)
-        if not self.name.startswith(site.login_base):
+        # allow preexisting slices to keep their original name for now
+        if not self.id and not self.name.startswith(site.login_base):
             raise ValidationError('slice name must begin with %s' % site.login_base)
         
         if self.serviceClass is None: