diff --git a/customfield/classes/data_controller.php b/customfield/classes/data_controller.php
index bd19792bd5f..49acf650953 100644
--- a/customfield/classes/data_controller.php
+++ b/customfield/classes/data_controller.php
@@ -238,7 +238,13 @@ abstract class data_controller {
      */
     protected function is_unique($value) : bool {
         global $DB;
+
+        // Ensure the "value" datafield can be safely compared across all databases.
         $datafield = $this->datafield();
+        if ($datafield === 'value') {
+            $datafield = $DB->sql_cast_to_char($datafield);
+        }
+
         $where = "fieldid = ? AND {$datafield} = ?";
         $params = [$this->get_field()->get('id'), $value];
         if ($this->get('id')) {
diff --git a/customfield/field/textarea/classes/data_controller.php b/customfield/field/textarea/classes/data_controller.php
index 64e62d1fce7..3d52fe15bc4 100644
--- a/customfield/field/textarea/classes/data_controller.php
+++ b/customfield/field/textarea/classes/data_controller.php
@@ -136,6 +136,29 @@ class data_controller extends \core_customfield\data_controller {
         $instance->{$this->get_form_element_name()} = $value;
     }
 
+    /**
+     * Checks if the value is empty, overriding the base method to ensure it's the "text" element of our value being compared
+     *
+     * @param mixed $value
+     * @return bool
+     */
+    protected function is_empty($value): bool {
+        if (is_array($value)) {
+            $value = $value['text'];
+        }
+        return html_is_blank($value);
+    }
+
+    /**
+     * Checks if the value is unique, overriding the base method to ensure it's the "text" element of our value being compared
+     *
+     * @param mixed $value
+     * @return bool
+     */
+    protected function is_unique($value): bool {
+        return parent::is_unique($value['text']);
+    }
+
     /**
      * Delete data
      *
@@ -166,9 +189,6 @@ class data_controller extends \core_customfield\data_controller {
         require_once($CFG->libdir . '/filelib.php');
 
         $value = $this->get_value();
-        if ($this->is_empty($value)) {
-            return null;
-        }
 
         if ($dataid = $this->get('id')) {
             $context = $this->get_context();