diff --git a/src/Symfony/Bridge/PhpUnit/DeprecationErrorHandler.php b/src/Symfony/Bridge/PhpUnit/DeprecationErrorHandler.php
index cbe405fa22bd..0ad463d56aaf 100644
--- a/src/Symfony/Bridge/PhpUnit/DeprecationErrorHandler.php
+++ b/src/Symfony/Bridge/PhpUnit/DeprecationErrorHandler.php
@@ -113,7 +113,7 @@ public static function collectDeprecations($outputFile)
                 $filesStack[] = $frame['file'];
             }
 
-            $deprecations[] = [error_reporting(), $msg, $file, $filesStack];
+            $deprecations[] = [error_reporting() & $type, $msg, $file, $filesStack];
 
             return null;
         });
@@ -143,7 +143,7 @@ public function handleError($type, $msg, $file, $line, $context = [])
             $method = $deprecation->originatingMethod();
             $msg = $deprecation->getMessage();
 
-            if (0 !== error_reporting()) {
+            if (error_reporting() & $type) {
                 $group = 'unsilenced';
             } elseif ($deprecation->isLegacy()) {
                 $group = 'legacy';
diff --git a/src/Symfony/Bridge/PhpUnit/Legacy/SymfonyTestsListenerTrait.php b/src/Symfony/Bridge/PhpUnit/Legacy/SymfonyTestsListenerTrait.php
index f9a1cadb4965..a67f02865696 100644
--- a/src/Symfony/Bridge/PhpUnit/Legacy/SymfonyTestsListenerTrait.php
+++ b/src/Symfony/Bridge/PhpUnit/Legacy/SymfonyTestsListenerTrait.php
@@ -310,7 +310,7 @@ public function handleError($type, $msg, $file, $line, $context = [])
         if (\is_array($parsedMsg)) {
             $msg = $parsedMsg['deprecation'];
         }
-        if (error_reporting()) {
+        if (error_reporting() & $type) {
             $msg = 'Unsilenced deprecation: '.$msg;
         }
         $this->gatheredDeprecations[] = $msg;
diff --git a/src/Symfony/Component/HttpKernel/Log/Logger.php b/src/Symfony/Component/HttpKernel/Log/Logger.php
index e3badc3676e6..1e6308d6e0ed 100644
--- a/src/Symfony/Component/HttpKernel/Log/Logger.php
+++ b/src/Symfony/Component/HttpKernel/Log/Logger.php
@@ -37,10 +37,10 @@ class Logger extends AbstractLogger
     private $formatter;
     private $handle;
 
-    public function __construct(string $minLevel = null, $output = 'php://stderr', callable $formatter = null)
+    public function __construct(string $minLevel = null, $output = null, callable $formatter = null)
     {
         if (null === $minLevel) {
-            $minLevel = 'php://stdout' === $output || 'php://stderr' === $output ? LogLevel::CRITICAL : LogLevel::WARNING;
+            $minLevel = null === $output || 'php://stdout' === $output || 'php://stderr' === $output ? LogLevel::ERROR : LogLevel::WARNING;
 
             if (isset($_ENV['SHELL_VERBOSITY']) || isset($_SERVER['SHELL_VERBOSITY'])) {
                 switch ((int) (isset($_ENV['SHELL_VERBOSITY']) ? $_ENV['SHELL_VERBOSITY'] : $_SERVER['SHELL_VERBOSITY'])) {
@@ -58,7 +58,7 @@ public function __construct(string $minLevel = null, $output = 'php://stderr', c
 
         $this->minLevelIndex = self::$levels[$minLevel];
         $this->formatter = $formatter ?: [$this, 'format'];
-        if (false === $this->handle = \is_resource($output) ? $output : @fopen($output, 'a')) {
+        if ($output && false === $this->handle = \is_resource($output) ? $output : @fopen($output, 'a')) {
             throw new InvalidArgumentException(sprintf('Unable to open "%s".', $output));
         }
     }
@@ -79,10 +79,14 @@ public function log($level, $message, array $context = [])
         }
 
         $formatter = $this->formatter;
-        @fwrite($this->handle, $formatter($level, $message, $context));
+        if ($this->handle) {
+            @fwrite($this->handle, $formatter($level, $message, $context));
+        } else {
+            error_log($formatter($level, $message, $context, false));
+        }
     }
 
-    private function format(string $level, string $message, array $context): string
+    private function format(string $level, string $message, array $context, bool $prefixDate = true): string
     {
         if (false !== strpos($message, '{')) {
             $replacements = [];
@@ -101,6 +105,11 @@ private function format(string $level, string $message, array $context): string
             $message = strtr($message, $replacements);
         }
 
-        return sprintf('%s [%s] %s', date(\DateTime::RFC3339), $level, $message).PHP_EOL;
+        $log = sprintf('[%s] %s', $level, $message).PHP_EOL;
+        if ($prefixDate) {
+            $log = date(\DateTime::RFC3339).' '.$log;
+        }
+
+        return $log;
     }
 }