diff --git a/interface/lib/classes/tform_base.inc.php b/interface/lib/classes/tform_base.inc.php
index 6de1ceeb9058f20b0314814be83e6d599ac2dedb..f6f669097563e4f3e596f612251628d2554c39ab 100644
--- a/interface/lib/classes/tform_base.inc.php
+++ b/interface/lib/classes/tform_base.inc.php
@@ -979,7 +979,7 @@ class tform_base {
 				break;
 			case 'ISINT':
 				if(function_exists('filter_var') && $field_value < 2147483647) {
-					if($field_value != '' && filter_var($field_value, FILTER_VALIDATE_INT) === false) {
+					if($field_value != '' && filter_var($field_value, FILTER_VALIDATE_INT, array("options" => array('min_range'=>0))) === false) {
 						$errmsg = $validator['errmsg'];
 						if(isset($this->wordbook[$errmsg])) {
 							$this->errorMessage .= $this->wordbook[$errmsg]."<br />\r\n";