diff --git a/b2g/config/gaia.json b/b2g/config/gaia.json
index c022c9dcb01a..a597c7892c5f 100644
--- a/b2g/config/gaia.json
+++ b/b2g/config/gaia.json
@@ -1,4 +1,4 @@
 {
-    "revision": "e4d8c96f60dc17c64cf5374ab4e7f030de585bfa", 
+    "revision": "dfacedfab9048c0b0e7235aa4d8a19714d5a8d54", 
     "repo_path": "/integration/gaia-central"
 }
diff --git a/dom/contacts/ContactManager.js b/dom/contacts/ContactManager.js
index d641f088108a..4224c2660ab2 100644
--- a/dom/contacts/ContactManager.js
+++ b/dom/contacts/ContactManager.js
@@ -4,7 +4,12 @@
 
 "use strict";
 
-const DEBUG = false;
+let DEBUG = false;
+
+function updateDebug(aResult) {
+  DEBUG = !!aResult;
+}
+
 function debug(s) { dump("-*- ContactManager: " + s + "\n"); }
 
 const Cc = Components.classes;
@@ -27,6 +32,10 @@ XPCOMUtils.defineLazyServiceGetter(this, "cpmm",
                                    "@mozilla.org/childprocessmessagemanager;1",
                                    "nsIMessageSender");
 
+XPCOMUtils.defineLazyServiceGetter(this, "gSettingsService",
+                                   "@mozilla.org/settingsService;1",
+                                   "nsISettingsService");
+
 const CONTACTS_SENDMORE_MINIMUM = 5;
 
 function stringOrBust(aObj) {
@@ -919,6 +928,16 @@ ContactManager.prototype = {
                               "PermissionPromptHelper:AskPermission:OK",
                               "Contacts:GetAll:Next", "Contacts:Revision",
                               "Contacts:Count"]);
+
+    let lock = gSettingsService.createLock();
+    lock.get("dom.mozContacts.debugging.enabled", {
+      handle: function(aName, aResult) {
+        updateDebug(aResult);
+      },
+      handleError: function(aErrorMessage) {
+        if (DEBUG) debug("Error reading dom.mozContacts.debugging.enabled setting: " + aErrorMessage);
+      }
+    });
   },
 
   // Called from DOMRequestIpcHelper
diff --git a/dom/contacts/fallback/ContactDB.jsm b/dom/contacts/fallback/ContactDB.jsm
index 7e9b51902e52..4f50733ad28c 100644
--- a/dom/contacts/fallback/ContactDB.jsm
+++ b/dom/contacts/fallback/ContactDB.jsm
@@ -6,7 +6,7 @@
 
 this.EXPORTED_SYMBOLS = ['ContactDB'];
 
-const DEBUG = false;
+let DEBUG = false;
 function debug(s) { dump("-*- ContactDB component: " + s + "\n"); }
 
 const Cu = Components.utils;
@@ -945,6 +945,10 @@ ContactDB.prototype = {
     this.substringMatching = aDigits;
   },
 
+  enableDebugging: function(aEnable) {
+    DEBUG = aEnable;
+  },
+
   init: function init(aGlobal) {
     this.initDBHelper(DB_NAME, DB_VERSION, [STORE_NAME, SAVED_GETALL_STORE_NAME, REVISION_STORE], aGlobal);
   }
diff --git a/dom/contacts/fallback/ContactService.jsm b/dom/contacts/fallback/ContactService.jsm
index 9bd5bc4dfb51..659da8c6ef95 100644
--- a/dom/contacts/fallback/ContactService.jsm
+++ b/dom/contacts/fallback/ContactService.jsm
@@ -4,7 +4,7 @@
 
 "use strict";
 
-const DEBUG = false;
+let DEBUG = false;
 function debug(s) { dump("-*- Fallback ContactService component: " + s + "\n"); }
 
 const Cu = Components.utils;
@@ -22,6 +22,10 @@ XPCOMUtils.defineLazyServiceGetter(this, "ppmm",
                                    "@mozilla.org/parentprocessmessagemanager;1",
                                    "nsIMessageListenerManager");
 
+XPCOMUtils.defineLazyServiceGetter(this, "gSettingsService",
+                                   "@mozilla.org/settingsService;1",
+                                   "nsISettingsService");
+
 let myGlobal = this;
 
 let ContactService = {
@@ -52,17 +56,33 @@ let ContactService = {
       }
     }
 
+    let lock = gSettingsService.createLock();
+    lock.get("dom.mozContacts.debugging.enabled", {
+      handle: function(aName, aResult) {
+        updateDebug(aResult);
+      },
+      handleError: function(aErrorMessage) {
+        if (DEBUG) debug("Error reading dom.mozContacts.debugging.enabled setting: " + aErrorMessage);
+      }
+    });
+
     Services.obs.addObserver(this, "profile-before-change", false);
+    Services.obs.addObserver(this, "mozsettings-changed", false);
     Services.prefs.addObserver("dom.phonenumber.substringmatching", this, false);
   },
 
+  enableDebugging: function(aResult) {
+    this._db.enableDebugging(aResult);
+  },
+
   observe: function(aSubject, aTopic, aData) {
-    if (aTopic === 'profile-before-change') {
+    if (aTopic === "profile-before-change") {
       myGlobal = null;
       this._messages.forEach(function(msgName) {
         ppmm.removeMessageListener(msgName, this);
       }.bind(this));
       Services.obs.removeObserver(this, "profile-before-change");
+      Services.obs.removeObserver(this, "mozsettings-changed");
       Services.prefs.removeObserver("dom.phonenumber.substringmatching", this);
       ppmm = null;
       this._messages = null;
@@ -71,7 +91,7 @@ let ContactService = {
       this._db = null;
       this._children = null;
       this._cursors = null;
-    } else if (aTopic === 'nsPref:changed' && aData.contains("dom.phonenumber.substringmatching")) {
+    } else if (aTopic === "nsPref:changed" && aData.contains("dom.phonenumber.substringmatching")) {
       // We don't fully support changing substringMatching during runtime. This is mostly for testing.
       let countryName = PhoneNumberUtils.getCountryName();
       if (Services.prefs.getPrefType("dom.phonenumber.substringmatching." + countryName) == Ci.nsIPrefBranch.PREF_INT) {
@@ -80,6 +100,11 @@ let ContactService = {
           this._db.enableSubstringMatching(val);
         }
       }
+    } else if (aTopic === "mozsettings-changed") {
+      let data = JSON.parse(aData);
+      if (data.key === "dom.mozContacts.debugging.enabled") {
+        updateDebug(data.value);
+      }
     }
   },
 
@@ -251,3 +276,8 @@ let ContactService = {
 }
 
 ContactService.init();
+
+function updateDebug(aResult) {
+  DEBUG = !!aResult;
+  ContactService.enableDebugging(DEBUG);
+}