diff --git a/addons/survey/static/src/js/survey.js b/addons/survey/static/src/js/survey.js
index 230003de673..f2d5e50fbbe 100644
--- a/addons/survey/static/src/js/survey.js
+++ b/addons/survey/static/src/js/survey.js
@@ -135,9 +135,11 @@ if(!the_form.length) {
             for (var i=0; i < date_fields.length; i++) {
                 var el = date_fields[i];
                 var moment_date = $(el).data('DateTimePicker').date();
-                moment_date.toJSON = function () {
-                    return this.clone().locale('en').format('YYYY-MM-DD');
-                };
+                if (moment_date) {
+                    moment_date.toJSON = function () {
+                        return this.clone().locale('en').format('YYYY-MM-DD');
+                    };
+                }
                 var field_obj = _.findWhere(formData, {'name': el.name});
                 field_obj.value = JSON.parse(JSON.stringify(moment_date));
             }