diff --git a/dom/mobileconnection/gonk/MobileConnectionService.js b/dom/mobileconnection/gonk/MobileConnectionService.js
index 332abc20314d..b88428fe8571 100644
--- a/dom/mobileconnection/gonk/MobileConnectionService.js
+++ b/dom/mobileconnection/gonk/MobileConnectionService.js
@@ -398,6 +398,7 @@ MobileConnectionProvider.prototype = {
         RIL.GECKO_SUPPORTED_NETWORK_TYPES_DEFAULT.split(",");
     }
 
+    let enumNetworkTypes = [];
     for (let type of supportedNetworkTypes) {
       // If the value in system property is not valid, use the default one which
       // is defined in ril_consts.js.
@@ -405,15 +406,18 @@ MobileConnectionProvider.prototype = {
         if (DEBUG) {
           this._debug("Unknown network type: " + type);
         }
-        supportedNetworkTypes =
-          RIL.GECKO_SUPPORTED_NETWORK_TYPES_DEFAULT.split(",");
+        RIL.GECKO_SUPPORTED_NETWORK_TYPES_DEFAULT.split(",").forEach(aType => {
+          enumNetworkTypes.push(RIL.GECKO_SUPPORTED_NETWORK_TYPES.indexOf(aType));
+        });
         break;
       }
+      enumNetworkTypes.push(RIL.GECKO_SUPPORTED_NETWORK_TYPES.indexOf(type));
     }
     if (DEBUG) {
-      this._debug("Supported Network Types: " + supportedNetworkTypes);
+      this._debug("Supported Network Types: " + enumNetworkTypes);
     }
-    return supportedNetworkTypes;
+
+    return enumNetworkTypes;
   },
 
   /**
diff --git a/dom/system/gonk/ril_consts.js b/dom/system/gonk/ril_consts.js
index 14f8eeaaf503..620f4f42ef37 100644
--- a/dom/system/gonk/ril_consts.js
+++ b/dom/system/gonk/ril_consts.js
@@ -427,6 +427,7 @@ this.RIL_PREFERRED_NETWORK_TYPE_TO_GECKO = [
 ];
 
 this.GECKO_SUPPORTED_NETWORK_TYPES_DEFAULT = "gsm,wcdma";
+// Index-item pair must be in sync with nsIMobileConnection.MOBILE_NETWORK_TYPE_*
 this.GECKO_SUPPORTED_NETWORK_TYPES = [
   "gsm",
   "wcdma",