diff --git a/plugins/system/fields/fields.php b/plugins/system/fields/fields.php
index ff889bb45421f..23afd468bd8e0 100644
--- a/plugins/system/fields/fields.php
+++ b/plugins/system/fields/fields.php
@@ -91,7 +91,7 @@ public function onContentAfterSave($context, $item, $isNew, $data = array())
 			$value = key_exists($field->name, $fieldsData) ? $fieldsData[$field->name] : null;
 
 			// JSON encode value for complex fields
-			if (is_array($value) && count($value, COUNT_NORMAL) !== count($value, COUNT_RECURSIVE))
+			if (is_array($value) && (count($value, COUNT_NORMAL) !== count($value, COUNT_RECURSIVE) || !count(array_filter(array_keys($value), 'is_numeric'))))
 			{
 				$value = json_encode($value);
 			}