diff --git a/lib/Doctrine/Common/Proxy/ProxyGenerator.php b/lib/Doctrine/Common/Proxy/ProxyGenerator.php
index 550407830..1cd7d79c5 100644
--- a/lib/Doctrine/Common/Proxy/ProxyGenerator.php
+++ b/lib/Doctrine/Common/Proxy/ProxyGenerator.php
@@ -941,7 +941,7 @@ private function isShortIdentifierGetter($method, ClassMetadata $class)
             && ($endLine - $startLine <= 4);
 
         if ($cheapCheck) {
-            $code = file($method->getFileName());
+            $code = file($method->getFileName() ? $method->getFileName():$method->getDeclaringClass()->getFileName());
             $code = trim(implode(' ', array_slice($code, $startLine - 1, $endLine - $startLine + 1)));
 
             $pattern = sprintf(self::PATTERN_MATCH_ID_METHOD, $method->getName(), $identifier);