diff --git a/inc/Db.php b/inc/Db.php
index 59fb4ce..62fa084 100644
--- a/inc/Db.php
+++ b/inc/Db.php
@@ -586,7 +586,8 @@ class Db extends PhpObject
 					{
 						if(is_array($asConstraints))
 						{
-							if(array_key_exists('constOpe', $asInfo) && array_key_exists($sField, $asInfo['constOpe']) && $asInfo['constOpe'][$sField]=='BETWEEN') {
+							$sConstOpe = $asInfo['constOpe'][$sField] ?? '';
+							if($sConstOpe == 'BETWEEN') {
 								//Between
 								$asSelection[$sField] = $asConstraints['from'].' AND '.$asConstraints['to'];
 								$asInfo['constOpe'][$sField] = " BETWEEN ";
@@ -594,7 +595,7 @@ class Db extends PhpObject
 							else {
 								//Multiple values (IN)
 								$asSelection[$sField] = "(".implode(', ', $asConstraints).")";
-								$asInfo['constOpe'][$sField] = " IN ";
+								$asInfo['constOpe'][$sField] = ($sConstOpe=='NOT IN')?" NOT IN ":" IN ";
 							}
 						}
 						elseif(!array_key_exists('constOpe', $asInfo) || !array_key_exists($sField, $asInfo['constOpe'])) $asInfo['constOpe'][$sField] = " = ";