gistfile1.txt

diff --git a/server/devpi_server/model.py b/server/devpi_server/model.py
--- a/server/devpi_server/model.py
+++ b/server/devpi_server/model.py
@@ -421,6 +421,10 @@ class PrivateStage(BaseStage):
 
     def modify(self, index=None, **kw):
         attrs = get_ixconfigattrs(self.xom.config.hook, self.ixconfig["type"])
+        if "type" in kw and kw["type"] not in ("mirror", "stage"):
+            raise InvalidIndexconfig(
+                ["invalid index type: %s" %(kw["type"],)])
+
         diff = list(set(kw).difference(attrs))
         if diff:
             raise InvalidIndexconfig(