diff --git a/tests/bootstrap.php b/tests/bootstrap.php
index 97c986fb3..db9555358 100644
--- a/tests/bootstrap.php
+++ b/tests/bootstrap.php
@@ -2,6 +2,7 @@
 
 namespace {
     \setlocale(\LC_ALL, 'C');
+    \error_reporting(E_ALL);
 }
 
 namespace GuzzleHttp\Test {