diff --git a/java/com/google/domain/registry/model/billing/BillingEvent.java b/java/com/google/domain/registry/model/billing/BillingEvent.java
index 1a18e56cf..163be565e 100644
--- a/java/com/google/domain/registry/model/billing/BillingEvent.java
+++ b/java/com/google/domain/registry/model/billing/BillingEvent.java
@@ -57,6 +57,7 @@ public abstract class BillingEvent extends ImmutableObject
     CREATE,
     TRANSFER,
     RENEW,
+    // TODO(b/27777398): Drop Reason.AUTO_RENEW after migration to Flag.AUTO_RENEW.
     AUTO_RENEW,
     RESTORE,
     SERVER_STATUS,
@@ -67,6 +68,7 @@ public abstract class BillingEvent extends ImmutableObject
   public enum Flag {
     ALLOCATION,
     ANCHOR_TENANT,
+    AUTO_RENEW,
     LANDRUSH,
     SUNRISE
   }
diff --git a/javatests/com/google/domain/registry/model/schema.txt b/javatests/com/google/domain/registry/model/schema.txt
index a8c32d76d..a6e7d604c 100644
--- a/javatests/com/google/domain/registry/model/schema.txt
+++ b/javatests/com/google/domain/registry/model/schema.txt
@@ -23,6 +23,7 @@ class com.google.domain.registry.model.billing.BillingEvent$Cancellation {
 enum com.google.domain.registry.model.billing.BillingEvent$Flag {
   ALLOCATION;
   ANCHOR_TENANT;
+  AUTO_RENEW;
   LANDRUSH;
   SUNRISE;
 }