diff --git a/mod/data/field/checkbox/field.class.php b/mod/data/field/checkbox/field.class.php
index 07112920f2b..fd486905e87 100644
--- a/mod/data/field/checkbox/field.class.php
+++ b/mod/data/field/checkbox/field.class.php
@@ -234,7 +234,7 @@ class data_field_checkbox extends data_field_base {
     function notemptyfield($value, $name) {
         $found = false;
         foreach ($value as $checkboxitem) {
-            if (!empty($checkboxitem)) {
+            if (strval($checkboxitem) !== '') {
                 $found = true;
                 break;
             }
diff --git a/mod/data/field/menu/field.class.php b/mod/data/field/menu/field.class.php
index 941576e1fc9..341149267e9 100644
--- a/mod/data/field/menu/field.class.php
+++ b/mod/data/field/menu/field.class.php
@@ -117,4 +117,15 @@ class data_field_menu extends data_field_base {
         return array(" ({$tablealias}.fieldid = {$this->field->id} AND $varcharcontent = :$name) ", array($name=>$value));
     }
 
+    /**
+     * Check if a field from an add form is empty
+     *
+     * @param mixed $value
+     * @param mixed $name
+     * @return bool
+     */
+    function notemptyfield($value, $name) {
+        return strval($value) !== '';
+    }
+
 }
diff --git a/mod/data/field/radiobutton/field.class.php b/mod/data/field/radiobutton/field.class.php
index 6e5b10de7fc..053d5037a6a 100644
--- a/mod/data/field/radiobutton/field.class.php
+++ b/mod/data/field/radiobutton/field.class.php
@@ -116,5 +116,15 @@ class data_field_radiobutton extends data_field_base {
         return array(" ({$tablealias}.fieldid = {$this->field->id} AND $varcharcontent = :$name) ", array($name=>$value));
     }
 
+    /**
+     * Check if a field from an add form is empty
+     *
+     * @param mixed $value
+     * @param mixed $name
+     * @return bool
+     */
+    function notemptyfield($value, $name) {
+        return strval($value) !== '';
+    }
 }