diff --git a/src/Symfony/Bridge/PhpUnit/DeprecationErrorHandler.php b/src/Symfony/Bridge/PhpUnit/DeprecationErrorHandler.php
index 28fea7aac9..efd1710292 100644
--- a/src/Symfony/Bridge/PhpUnit/DeprecationErrorHandler.php
+++ b/src/Symfony/Bridge/PhpUnit/DeprecationErrorHandler.php
@@ -111,7 +111,7 @@ class DeprecationErrorHandler
 
                     exit(1);
                 }
-                if ('legacy' !== $group && self::MODE_WEAK !== $mode) {
+                if ('legacy' !== $group && DeprecationErrorHandler::MODE_WEAK !== $mode) {
                     $ref = &$deprecations[$group][$msg]['count'];
                     ++$ref;
                     $ref = &$deprecations[$group][$msg][$class.'::'.$method];
@@ -131,7 +131,7 @@ class DeprecationErrorHandler
                 restore_error_handler();
                 self::register($mode);
             }
-        } elseif (!isset($mode[0]) || '/' !== $mode[0]) {
+        } else {
             self::$isRegistered = true;
             if (self::hasColorSupport()) {
                 $colorize = function ($str, $red) {
@@ -144,6 +144,9 @@ class DeprecationErrorHandler
             }
             register_shutdown_function(function () use ($getMode, &$deprecations, $deprecationHandler, $colorize) {
                 $mode = $getMode();
+                if (isset($mode[0]) && '/' === $mode[0]) {
+                    return;
+                }
                 $currErrorHandler = set_error_handler('var_dump');
                 restore_error_handler();