diff --git a/src/com/android/phone/CdmaCallOptions.java b/src/com/android/phone/CdmaCallOptions.java
index 40e3517..6145870 100644
--- a/src/com/android/phone/CdmaCallOptions.java
+++ b/src/com/android/phone/CdmaCallOptions.java
@@ -21,18 +21,37 @@
 import android.preference.Preference;
 import android.preference.PreferenceScreen;
 import android.telephony.CarrierConfigManager;
+import android.telephony.SubscriptionManager;
+import android.telephony.ims.ImsException;
+import android.telephony.ims.ImsManager;
+import android.telephony.ims.ImsMmTelManager;
+import android.telephony.ims.feature.MmTelFeature;
+import android.util.Log;
 import android.view.MenuItem;
 
 import com.android.internal.telephony.PhoneConstants;
 
 public class CdmaCallOptions extends TimeConsumingPreferenceActivity {
     private static final String LOG_TAG = "CdmaCallOptions";
-    private final boolean DBG = (PhoneGlobals.DBG_LEVEL >= 2);
 
     private static final String BUTTON_VP_KEY = "button_voice_privacy_key";
     private static final String CALL_FORWARDING_KEY = "call_forwarding_key";
     private static final String CALL_WAITING_KEY = "call_waiting_key";
 
+    private class UtCallback extends ImsMmTelManager.CapabilityCallback {
+        @Override
+        public void onCapabilitiesStatusChanged(MmTelFeature.MmTelCapabilities capabilities) {
+            boolean isUtAvailable = capabilities.isCapable(
+                    MmTelFeature.MmTelCapabilities.CAPABILITY_TYPE_UT);
+            updatePreferencesEnabled(isUtAvailable);
+        }
+    }
+
+    private Preference mCallForwardingPref;
+    private CdmaCallWaitingPreference mCallWaitingPref;
+    private UtCallback mUtCallback;
+    private ImsMmTelManager mMmTelManager;
+
     @Override
     protected void onCreate(Bundle icicle) {
         super.onCreate(icicle);
@@ -47,33 +66,107 @@
                 (CdmaVoicePrivacySwitchPreference) findPreference(BUTTON_VP_KEY);
         buttonVoicePrivacy.setPhone(subInfoHelper.getPhone());
         PersistableBundle carrierConfig;
+        int subId;
         if (subInfoHelper.hasSubId()) {
-            carrierConfig = PhoneGlobals.getInstance().getCarrierConfigForSubId(
-                    subInfoHelper.getSubId());
+            subId = subInfoHelper.getSubId();
         } else {
-            carrierConfig = PhoneGlobals.getInstance().getCarrierConfig();
+            subId = SubscriptionManager.getDefaultSubscriptionId();
         }
+        carrierConfig = PhoneGlobals.getInstance().getCarrierConfigForSubId(subId);
         if (subInfoHelper.getPhone().getPhoneType() != PhoneConstants.PHONE_TYPE_CDMA
                 || carrierConfig.getBoolean(CarrierConfigManager.KEY_VOICE_PRIVACY_DISABLE_UI_BOOL)) {
             buttonVoicePrivacy.setEnabled(false);
         }
 
-        Preference callForwardingPref = getPreferenceScreen().findPreference(CALL_FORWARDING_KEY);
+        mCallForwardingPref = getPreferenceScreen().findPreference(CALL_FORWARDING_KEY);
         if (carrierConfig != null && carrierConfig.getBoolean(
                 CarrierConfigManager.KEY_CALL_FORWARDING_VISIBILITY_BOOL)) {
-            callForwardingPref.setIntent(
+            mCallForwardingPref.setIntent(
                     subInfoHelper.getIntent(CdmaCallForwardOptions.class));
         } else {
-            getPreferenceScreen().removePreference(callForwardingPref);
+            getPreferenceScreen().removePreference(mCallForwardingPref);
+            mCallForwardingPref = null;
         }
 
-        CdmaCallWaitingPreference callWaitingPref = (CdmaCallWaitingPreference)getPreferenceScreen()
-                                                     .findPreference(CALL_WAITING_KEY);
-        if (carrierConfig != null && carrierConfig.getBoolean(
+        mCallWaitingPref = (CdmaCallWaitingPreference) getPreferenceScreen()
+                .findPreference(CALL_WAITING_KEY);
+        if (carrierConfig == null || !carrierConfig.getBoolean(
                 CarrierConfigManager.KEY_ADDITIONAL_SETTINGS_CALL_WAITING_VISIBILITY_BOOL)) {
-            callWaitingPref.init(this, subInfoHelper.getPhone());
+            getPreferenceScreen().removePreference(mCallWaitingPref);
+            mCallWaitingPref = null;
+        }
+        // Do not go further if the preferences are removed.
+        if (mCallForwardingPref == null && mCallWaitingPref == null) return;
+
+        boolean isSsOverCdmaEnabled = carrierConfig != null && carrierConfig.getBoolean(
+                CarrierConfigManager.KEY_SUPPORT_SS_OVER_CDMA_BOOL);
+        boolean isSsOverUtEnabled = carrierConfig != null && carrierConfig.getBoolean(
+                CarrierConfigManager.KEY_CARRIER_SUPPORTS_SS_OVER_UT_BOOL);
+
+        if (isSsOverCdmaEnabled && mCallWaitingPref != null) {
+            // If SS over CDMA is enabled, then the preference will always be enabled,
+            // independent of SS over UT status. Initialize it now.
+            mCallWaitingPref.init(this, subInfoHelper.getPhone());
+            return;
+        }
+        // Since SS over UT availability can change, first disable the preferences that rely on it
+        // and only enable it if UT is available.
+        updatePreferencesEnabled(false);
+        if (isSsOverUtEnabled) {
+            // Register a callback to listen to SS over UT state. This will enable the preferences
+            // once the callback notifies settings that UT is enabled.
+            registerMmTelCapsCallback(subId);
         } else {
-            getPreferenceScreen().removePreference(callWaitingPref);
+            Log.w(LOG_TAG, "SS over UT and CDMA disabled, but preferences are visible.");
+        }
+    }
+
+    @Override
+    public void onStop() {
+        super.onStop();
+        unregisterMmTelCapsCallback();
+    }
+
+    private void unregisterMmTelCapsCallback() {
+        if (mMmTelManager == null || mUtCallback == null) return;
+        mMmTelManager.unregisterMmTelCapabilityCallback(mUtCallback);
+        mUtCallback = null;
+        Log.d(LOG_TAG, "unregisterMmTelCapsCallback: UT availability callback unregistered");
+    }
+
+    private void registerMmTelCapsCallback(int subId) {
+        if (!SubscriptionManager.isValidSubscriptionId(subId)) return;
+        ImsManager imsManager = getSystemService(ImsManager.class);
+        try {
+            if (imsManager != null) {
+                mUtCallback = new UtCallback();
+                mMmTelManager = imsManager.getImsMmTelManager(subId);
+                // Callback will call back with the state as soon as it is available.
+                mMmTelManager.registerMmTelCapabilityCallback(getMainExecutor(), mUtCallback);
+                Log.d(LOG_TAG, "registerMmTelCapsCallback: UT availability callback "
+                        + "registered");
+            } else {
+                Log.w(LOG_TAG, "registerMmTelCapsCallback: couldn't get ImsManager, assuming "
+                        + "UT is not available: ");
+                updatePreferencesEnabled(false);
+            }
+        } catch (IllegalArgumentException | ImsException e) {
+            Log.w(LOG_TAG, "registerMmTelCapsCallback: couldn't register callback, assuming "
+                    + "UT is not available: " + e);
+            updatePreferencesEnabled(false);
+        }
+    }
+
+    private void updatePreferencesEnabled(boolean isEnabled) {
+        Log.d(LOG_TAG, "updatePreferencesEnabled: " + isEnabled);
+        if (mCallForwardingPref != null) mCallForwardingPref.setEnabled(isEnabled);
+
+        if (mCallWaitingPref == null || mCallWaitingPref.isEnabled() == isEnabled) return;
+        mCallWaitingPref.setActionAvailable(isEnabled);
+        if (isEnabled) {
+            SubscriptionInfoHelper subInfoHelper = new SubscriptionInfoHelper(this, getIntent());
+            // kick off the normal process to populate the Call Waiting status.
+            mCallWaitingPref.init(this, subInfoHelper.getPhone());
         }
     }
 
diff --git a/src/com/android/phone/CdmaCallWaitingPreference.java b/src/com/android/phone/CdmaCallWaitingPreference.java
index 4cda7ba..3713b19 100644
--- a/src/com/android/phone/CdmaCallWaitingPreference.java
+++ b/src/com/android/phone/CdmaCallWaitingPreference.java
@@ -16,32 +16,29 @@
 
 package com.android.phone;
 
-import com.android.internal.telephony.CommandException;
-import com.android.internal.telephony.CommandsInterface;
-import com.android.internal.telephony.Phone;
-
 import android.app.AlertDialog;
 import android.content.Context;
 import android.content.DialogInterface;
-import android.content.res.TypedArray;
 import android.os.AsyncResult;
 import android.os.Handler;
 import android.os.Message;
 import android.preference.Preference;
-import android.preference.PreferenceActivity;
 import android.util.AttributeSet;
 import android.util.Log;
 
+import com.android.internal.telephony.CommandException;
+import com.android.internal.telephony.CommandsInterface;
+import com.android.internal.telephony.Phone;
+
 public class CdmaCallWaitingPreference extends Preference {
     private static final String LOG_TAG = "CdmaCallWaitingPreference";
     private static final boolean DBG = (PhoneGlobals.DBG_LEVEL >= 2);
 
-    private int mButtonClicked;
     private Context mContext;
     private Phone mPhone;
-    private SubscriptionInfoHelper mSubscriptionInfoHelper;
     private TimeConsumingPreferenceListener mTcpListener;
     private MyHandler mHandler = new MyHandler();
+    private boolean mIsActionAvailable = true;
 
     public CdmaCallWaitingPreference(Context context, AttributeSet attrs, int defStyleAttr) {
         super(context, attrs, defStyleAttr);
@@ -67,6 +64,16 @@
         }
     }
 
+    /**
+     * Enables this preference if Call waiting is available in the platform. If not, this will
+     * override all attempts to enable the preference from the associated
+     * TimeConsumingPreferenceActivity.
+     */
+    public void setActionAvailable(boolean isAvailable) {
+        mIsActionAvailable = isAvailable;
+        super.setEnabled(mIsActionAvailable);
+    }
+
     @Override
     public void onClick() {
         super.onClick();
@@ -95,6 +102,14 @@
         builder.create().show();
     }
 
+    @Override
+    public void setEnabled(boolean enabled) {
+        // If this action is currently disabled due to configuration changes, do not allow anything
+        // to enable it.
+        if (!mIsActionAvailable) return;
+        super.setEnabled(enabled);
+    }
+
     private class MyHandler extends Handler {
         static final int MESSAGE_GET_CALL_WAITING = 0;
         static final int MESSAGE_SET_CALL_WAITING = 1;