diff --git a/telecomm/java/android/telecom/Call.java b/telecomm/java/android/telecom/Call.java
index d94fafc..980ea5c 100644
--- a/telecomm/java/android/telecom/Call.java
+++ b/telecomm/java/android/telecom/Call.java
@@ -1476,12 +1476,21 @@
         /**
          * Invoked when the RTT session failed to initiate for some reason, including rejection
          * by the remote party.
+         * <p>
+         * This callback will ONLY be invoked to report a failure related to a user initiated
+         * session modification request (i.e. {@link Call#sendRttRequest()}).
+         * <p>
+         * If a call is initiated with {@link TelecomManager#EXTRA_START_CALL_WITH_RTT} specified,
+         * the availability of RTT can be determined by checking {@link Details#PROPERTY_RTT}
+         * once the call enters state {@link Details#STATE_ACTIVE}.
+         *
          * @param call The call which the RTT initiation failure occurred on.
          * @param reason One of the status codes defined in
-         *               {@link android.telecom.Connection.RttModifyStatus}, with the exception of
-         *               {@link android.telecom.Connection.RttModifyStatus#SESSION_MODIFY_REQUEST_SUCCESS}.
+         *      {@link android.telecom.Connection.RttModifyStatus}, with the exception of
+         *      {@link android.telecom.Connection.RttModifyStatus#SESSION_MODIFY_REQUEST_SUCCESS}.
          */
-        public void onRttInitiationFailure(Call call, int reason) {}
+        public void onRttInitiationFailure(Call call,
+                @android.telecom.Connection.RttModifyStatus.RttSessionModifyStatus int reason) {}
 
         /**
          * Invoked when Call handover from one {@link PhoneAccount} to other {@link PhoneAccount}
diff --git a/telecomm/java/android/telecom/Connection.java b/telecomm/java/android/telecom/Connection.java
index 467084a..21c6b47 100644
--- a/telecomm/java/android/telecom/Connection.java
+++ b/telecomm/java/android/telecom/Connection.java
@@ -1399,6 +1399,18 @@
          * Session modify request rejected by remote user.
          */
         public static final int SESSION_MODIFY_REQUEST_REJECTED_BY_REMOTE = 5;
+
+
+        /**@hide*/
+        @Retention(RetentionPolicy.SOURCE)
+        @IntDef(prefix = "SESSION_MODIFY_REQUEST_", value = {
+                SESSION_MODIFY_REQUEST_SUCCESS,
+                SESSION_MODIFY_REQUEST_FAIL,
+                SESSION_MODIFY_REQUEST_INVALID,
+                SESSION_MODIFY_REQUEST_TIMED_OUT,
+                SESSION_MODIFY_REQUEST_REJECTED_BY_REMOTE
+        })
+        public @interface RttSessionModifyStatus {}
     }
 
     /**