diff --git a/dom/nfc/nsNfc.js b/dom/nfc/nsNfc.js
index 78c88167333..7033155ba7d 100644
--- a/dom/nfc/nsNfc.js
+++ b/dom/nfc/nsNfc.js
@@ -192,6 +192,10 @@ MozNFCTagImpl.prototype = {
     return callback.promise;
   },
 
+  notifyLost: function notifyLost() {
+    this.isLost = true;
+  },
+
   classID: Components.ID("{4e1e2e90-3137-11e3-aa6e-0800200c9a66}"),
   contractID: "@mozilla.org/nfc/tag;1",
   QueryInterface: XPCOMUtils.generateQI([Ci.nsISupports,
@@ -244,6 +248,10 @@ MozNFCPeerImpl.prototype = {
     return callback.promise;
   },
 
+  notifyLost: function notifyLost() {
+    this.isLost = true;
+  },
+
   classID: Components.ID("{c1b2bcf0-35eb-11e3-aa6e-0800200c9a66}"),
   contractID: "@mozilla.org/nfc/peer;1",
   QueryInterface: XPCOMUtils.generateQI([Ci.nsISupports,
@@ -432,7 +440,7 @@ MozNFCImpl.prototype = {
         this, /* useCapture */false);
     }
 
-    this.nfcTag.isLost = true;
+    this.nfcTag.notifyLost();
     this.nfcTag = null;
 
     debug("fire ontaglost " + sessionToken);
@@ -491,7 +499,7 @@ MozNFCImpl.prototype = {
         this, /* useCapture */false);
     }
 
-    this.nfcPeer.isLost = true;
+    this.nfcPeer.notifyLost();
     this.nfcPeer = null;
 
     debug("fire onpeerlost");
diff --git a/dom/webidl/MozNFCPeer.webidl b/dom/webidl/MozNFCPeer.webidl
index a98b7a635c5..1ab4bccce2e 100644
--- a/dom/webidl/MozNFCPeer.webidl
+++ b/dom/webidl/MozNFCPeer.webidl
@@ -10,6 +10,11 @@
 
 [JSImplementation="@mozilla.org/nfc/peer;1", AvailableIn="PrivilegedApps"]
 interface MozNFCPeer {
+  /**
+   * Indicate if this peer is already lost.
+   */
+  readonly attribute boolean isLost;
+
   /**
    * Send NDEF data to peer device.
    */
@@ -28,8 +33,6 @@ partial interface MozNFCPeer {
   [ChromeOnly]
   attribute DOMString session;
 
-  /**
-   * Indicate if this peer is already lost.
-   */
-  readonly attribute boolean isLost;
+  [ChromeOnly]
+  void notifyLost();
 };
diff --git a/dom/webidl/MozNFCTag.webidl b/dom/webidl/MozNFCTag.webidl
index 07b31ab1f2c..07f564b4ef0 100644
--- a/dom/webidl/MozNFCTag.webidl
+++ b/dom/webidl/MozNFCTag.webidl
@@ -72,6 +72,11 @@ interface MozNFCTag {
    */
   readonly attribute boolean? canBeMadeReadOnly;
 
+  /**
+   * Indicate if this tag is already lost.
+   */
+  readonly attribute boolean isLost;
+
   /**
    * Read current NDEF data on the tag.
    */
@@ -102,8 +107,6 @@ partial interface MozNFCTag {
   [ChromeOnly]
   attribute DOMString session;
 
-  /**
-   * Indicate if this tag is already lost.
-   */
-  readonly attribute boolean isLost;
+  [ChromeOnly]
+  void notifyLost();
 };