--- a/b2g/chrome/content/forms.js
+++ b/b2g/chrome/content/forms.js
@@ -107,19 +107,24 @@ let FormAssistant = {
   receiveMessage: function fa_receiveMessage(msg) {
     let target = this.previousTarget;
     if (!target) {
       return;
     }
 
     let json = msg.json;
     switch (msg.name) {
-      case "Forms:Input:Value":
+      case "Forms:Input:Value": {
         target.value = json.value;
+
+        let event = content.document.createEvent('HTMLEvents');
+        event.initEvent('input', true, false);
+        target.dispatchEvent(event);
         break;
+      }
 
       case "Forms:Select:Choice":
         let options = target.options;
         let valueChanged = false;
         if ("index" in json) {
           if (options.selectedIndex != json.index) {
             options.selectedIndex = json.index;
             valueChanged = true;