diff --git a/telephony/java/android/telephony/data/DataCallResponse.java b/telephony/java/android/telephony/data/DataCallResponse.java
index 39859b1e4fdb0..579200e15cca4 100644
--- a/telephony/java/android/telephony/data/DataCallResponse.java
+++ b/telephony/java/android/telephony/data/DataCallResponse.java
@@ -69,6 +69,7 @@ public final class DataCallResponse implements Parcelable {
 
     /** {@hide} */
     @IntDef(prefix = "HANDOVER_FAILURE_MODE_", value = {
+            HANDOVER_FAILURE_MODE_UNKNOWN,
             HANDOVER_FAILURE_MODE_LEGACY,
             HANDOVER_FAILURE_MODE_DO_FALLBACK,
             HANDOVER_FAILURE_MODE_NO_FALLBACK_RETRY_HANDOVER,