diff --git a/telephony/java/android/telephony/CarrierConfigManager.java b/telephony/java/android/telephony/CarrierConfigManager.java
index 4cc7097ac3f3f..7c0118c4c8691 100755
--- a/telephony/java/android/telephony/CarrierConfigManager.java
+++ b/telephony/java/android/telephony/CarrierConfigManager.java
@@ -467,6 +467,14 @@ public class CarrierConfigManager {
     public static final String KEY_NOTIFY_HANDOVER_VIDEO_FROM_WIFI_TO_LTE_BOOL =
             "notify_handover_video_from_wifi_to_lte_bool";
 
+    /**
+     * Flag specifying whether the carrier supports merging a RTT call with a voice call,
+     * downgrading the call in the process.
+     * @hide
+     */
+    public static final String KEY_ALLOW_MERGING_RTT_CALLS_BOOL =
+             "allow_merging_rtt_calls_bool";
+
     /**
      * Flag specifying whether the carrier wants to notify the user when a VT call has been handed
      * over from LTE to WIFI.
@@ -3114,6 +3122,7 @@ public class CarrierConfigManager {
         sDefaults.putBoolean(KEY_CARRIER_VOLTE_AVAILABLE_BOOL, false);
         sDefaults.putBoolean(KEY_CARRIER_VT_AVAILABLE_BOOL, false);
         sDefaults.putBoolean(KEY_NOTIFY_HANDOVER_VIDEO_FROM_WIFI_TO_LTE_BOOL, false);
+        sDefaults.putBoolean(KEY_ALLOW_MERGING_RTT_CALLS_BOOL, false);
         sDefaults.putBoolean(KEY_NOTIFY_HANDOVER_VIDEO_FROM_LTE_TO_WIFI_BOOL, false);
         sDefaults.putBoolean(KEY_SUPPORT_DOWNGRADE_VT_TO_AUDIO_BOOL, true);
         sDefaults.putString(KEY_DEFAULT_VM_NUMBER_STRING, "");