diff --git a/test/phpunit/FilesLibTest.php b/test/phpunit/FilesLibTest.php
index c625b1f3e51..d38f73326b2 100644
--- a/test/phpunit/FilesLibTest.php
+++ b/test/phpunit/FilesLibTest.php
@@ -316,7 +316,7 @@ class FilesLibTest extends PHPUnit_Framework_TestCase
 
         $result=dol_copy($file, $conf->admin->dir_temp.'/file.csv',0,1);
         print __METHOD__." result=".$result."\n";
-        $this->assertGreaterThanOrEqual(1,$result, 'copy into a dir that exists');    // Should be 1
+        $this->assertGreaterThanOrEqual(1,$result, 'copy file ('.$file.') into a dir that exists ('.$conf->admin->dir_temp.'/file.csv'.')');    // Should be 1
 
         // Again to test with overwriting=0
         $result=dol_copy($file, $conf->admin->dir_temp.'/file.csv',0,0);