diff --git a/metropolis/proto/common/common.proto b/metropolis/proto/common/common.proto
index fc461ab..653b0d2 100644
--- a/metropolis/proto/common/common.proto
+++ b/metropolis/proto/common/common.proto
@@ -172,7 +172,8 @@
 // directory.
 message ClusterDirectory {
     message Node {
-        bytes public_key = 1;
+        string id = 3;
+        reserved 1;
         message Address {
             string host = 1;
         };