diff --git a/src/com/android/phone/PhoneInterfaceManager.java b/src/com/android/phone/PhoneInterfaceManager.java
index 5cbb6f6..2d7ef74 100755
--- a/src/com/android/phone/PhoneInterfaceManager.java
+++ b/src/com/android/phone/PhoneInterfaceManager.java
@@ -3364,6 +3364,11 @@
         return isCarrierSupported && isDeviceSupported;
     }
 
+    public boolean isRttEnabled() {
+        return isRttSupported() && Settings.Secure.getInt(mPhone.getContext().getContentResolver(),
+                Settings.Secure.RTT_CALLING_MODE, 0) != 0;
+    }
+
     /**
      * Returns the unique device ID of phone, for example, the IMEI for
      * GSM and the MEID for CDMA phones. Return null if device ID is not available.
diff --git a/src/com/android/services/telephony/TelecomAccountRegistry.java b/src/com/android/services/telephony/TelecomAccountRegistry.java
index 13b0494..6c8dcaa 100644
--- a/src/com/android/services/telephony/TelecomAccountRegistry.java
+++ b/src/com/android/services/telephony/TelecomAccountRegistry.java
@@ -22,6 +22,7 @@
 import android.content.Intent;
 import android.content.IntentFilter;
 import android.content.res.Resources;
+import android.database.ContentObserver;
 import android.graphics.Bitmap;
 import android.graphics.Canvas;
 import android.graphics.PorterDuff;
@@ -29,9 +30,12 @@
 import android.graphics.drawable.Icon;
 import android.net.Uri;
 import android.os.Bundle;
+import android.os.Handler;
+import android.os.Looper;
 import android.os.PersistableBundle;
 import android.os.UserHandle;
 import android.os.UserManager;
+import android.provider.Settings;
 import android.telecom.PhoneAccount;
 import android.telecom.PhoneAccountHandle;
 import android.telecom.TelecomManager;
@@ -234,7 +238,7 @@
                 extras.putBoolean(PhoneAccount.EXTRA_PLAY_CALL_RECORDING_TONE, true);
             }
 
-            if (PhoneGlobals.getInstance().phoneMgr.isRttSupported()) {
+            if (PhoneGlobals.getInstance().phoneMgr.isRttEnabled()) {
                 capabilities |= PhoneAccount.CAPABILITY_RTT;
             }
 
@@ -497,6 +501,13 @@
             }
         }
 
+        public void updateRttCapability() {
+            boolean isRttEnabled = PhoneGlobals.getInstance().phoneMgr.isRttEnabled();
+            boolean oldRttEnabled = mAccount.hasCapabilities(PhoneAccount.CAPABILITY_RTT);
+            if (isRttEnabled != oldRttEnabled) {
+                mAccount = registerPstnPhoneAccount(mIsEmergency, mIsDummy);
+            }
+        }
         /**
          * Indicates whether this account supports pausing video calls.
          * @return {@code true} if the account supports pausing video calls, {@code false}
@@ -602,7 +613,7 @@
     private final TelephonyManager mTelephonyManager;
     private final SubscriptionManager mSubscriptionManager;
     private List<AccountEntry> mAccounts = new LinkedList<AccountEntry>();
-    private Object mAccountsLock = new Object();
+    private final Object mAccountsLock = new Object();
     private int mServiceState = ServiceState.STATE_POWER_OFF;
     private boolean mIsPrimaryUser = true;
 
@@ -805,6 +816,23 @@
         // use is not the primary user we disable video calling.
         mContext.registerReceiver(mUserSwitchedReceiver,
                 new IntentFilter(Intent.ACTION_USER_SWITCHED));
+
+        // Listen to the RTT system setting so that we update it when the user flips it.
+        ContentObserver rttUiSettingObserver = new ContentObserver(
+                new Handler(Looper.getMainLooper())) {
+            @Override
+            public void onChange(boolean selfChange) {
+                synchronized (mAccountsLock) {
+                    for (AccountEntry account : mAccounts) {
+                        account.updateRttCapability();
+                    }
+                }
+            }
+        };
+
+        Uri rttSettingUri = Settings.Secure.getUriFor(Settings.Secure.RTT_CALLING_MODE);
+        mContext.getContentResolver().registerContentObserver(
+                rttSettingUri, false, rttUiSettingObserver);
     }
 
     /**