diff --git a/setup/compiler.class.inc.php b/setup/compiler.class.inc.php
index 7a17e178f..26d333753 100644
--- a/setup/compiler.class.inc.php
+++ b/setup/compiler.class.inc.php
@@ -633,7 +633,7 @@ EOF;
 				$aParameters['allowed_values'] = 'null'; // or "new ValueSetEnum('SELECT xxxx')"
 				$aParameters['sql'] = $this->GetPropString($oField, 'sql', '');
 				$aParameters['default_value'] = $this->GetPropString($oField, 'default_value', '');
-				$aParameters['is_null_allowed'] = $oField->GetChildText('is_null_allowed', false);
+				$aParameters['is_null_allowed'] = $this->GetPropBoolean($oField, 'is_null_allowed', false);
 				$aParameters['depends_on'] = $sDependencies;
 			}