diff --git a/src/Propel/Generator/Manager/AbstractManager.php b/src/Propel/Generator/Manager/AbstractManager.php
index 869e928608..2581258289 100644
--- a/src/Propel/Generator/Manager/AbstractManager.php
+++ b/src/Propel/Generator/Manager/AbstractManager.php
@@ -374,7 +374,7 @@ protected function includeExternalSchemas(\DOMDocument $dom, $srcDir)
             // The external schema may have external schemas of its own ; recurs
             $this->includeExternalSchemas($externalSchemaDom, $srcDir);
             foreach ($externalSchemaDom->getElementsByTagName('table') as $tableNode) {
-                if ($referenceOnly) {
+                if ("true" === $referenceOnly) {
                     $tableNode->setAttribute("skipSql", "true");
                 }
                 $databaseNode->appendChild($dom->importNode($tableNode, true));