diff --git a/service/src/main/proto/KeyTransparencyService.proto b/service/src/main/proto/KeyTransparencyService.proto
index a4ba7b8c9..4cde293fe 100644
--- a/service/src/main/proto/KeyTransparencyService.proto
+++ b/service/src/main/proto/KeyTransparencyService.proto
@@ -182,14 +182,14 @@ message FullTreeHead {
    * A representation of the log tree's current state signed by the key transparency service.
    */
   TreeHead tree_head = 1;
-  /**
-   * A consistency proof between the current tree size and the requested distinguished tree size.
-   */
-  repeated bytes distinguished = 2;
   /**
    * A consistency proof between the current tree size and the requested tree size.
    */
-  repeated bytes consistency = 3;
+  repeated bytes last = 2;
+  /**
+   * A consistency proof between the current tree size and the requested distinguished tree size.
+   */
+  repeated bytes distinguished = 3;
   /**
    * A tree head signed by a third-party auditor.
    */