diff --git a/src/Symfony/Component/ClassLoader/ClassLoader.php b/src/Symfony/Component/ClassLoader/ClassLoader.php
index a2038a0d9f8c..9d3b72e3ee75 100644
--- a/src/Symfony/Component/ClassLoader/ClassLoader.php
+++ b/src/Symfony/Component/ClassLoader/ClassLoader.php
@@ -181,7 +181,7 @@ public function findFile($class)
         $classPath .= str_replace('_', DIRECTORY_SEPARATOR, $className) . '.php';
 
         foreach ($this->prefixes as $prefix => $dirs) {
-            if (0 === strpos($class, $prefix)) {
+            if ($class === strstr($class, $prefix)) {
                 foreach ($dirs as $dir) {
                     if (file_exists($dir . DIRECTORY_SEPARATOR . $classPath)) {
                         return $dir . DIRECTORY_SEPARATOR . $classPath;