diff --git a/Civi/DataProcessor/DataFlow/SqlDataFlow/SimpleWhereClause.php b/Civi/DataProcessor/DataFlow/SqlDataFlow/SimpleWhereClause.php
index 2854e1f0221157ba3d5116e9894e9f45d00f69b6..f59d1a085d986a9126e18b0976cc5be3da6e4e99 100644
--- a/Civi/DataProcessor/DataFlow/SqlDataFlow/SimpleWhereClause.php
+++ b/Civi/DataProcessor/DataFlow/SqlDataFlow/SimpleWhereClause.php
@@ -109,7 +109,7 @@ class SimpleWhereClause implements WhereClauseInterface {
         return "(`{$this->table_alias}`.`{$this->field}` {$this->operator} {$this->value} OR `{$this->table_alias}`.`{$this->field}` IS NULL)";
         break;
       case 'IS NULL':
-        return "(`{$this->table_alias}`.`{$this->field}` {$this->operator} OR {$this->table_alias}`.`{$this->field} != '')";
+        return "(`{$this->table_alias}`.`{$this->field}` {$this->operator} OR `{$this->table_alias}`.`{$this->field} != '')";
         break;
       case 'IS NOT NULL':
         return "(`{$this->table_alias}`.`{$this->field}` {$this->operator} AND `{$this->table_alias}`.`{$this->field}` != '')";