diff --git a/src/Monolog/Handler/ChromePHPHandler.php b/src/Monolog/Handler/ChromePHPHandler.php
index ee92e3ca..75fa8025 100644
--- a/src/Monolog/Handler/ChromePHPHandler.php
+++ b/src/Monolog/Handler/ChromePHPHandler.php
@@ -155,8 +155,11 @@ class ChromePHPHandler extends AbstractProcessingHandler
      */
     protected function headersAccepted()
     {
-        return !isset($_SERVER['HTTP_USER_AGENT'])
-               || preg_match('{\bChrome/\d+[\.\d+]*\b}', $_SERVER['HTTP_USER_AGENT']);
+        if (empty($_SERVER['HTTP_USER_AGENT'])) {
+            return false;
+        }
+
+        return preg_match('{\bChrome/\d+[\.\d+]*\b}', $_SERVER['HTTP_USER_AGENT']);
     }
 
     /**
diff --git a/src/Monolog/Handler/FirePHPHandler.php b/src/Monolog/Handler/FirePHPHandler.php
index b233f14c..68dbc185 100644
--- a/src/Monolog/Handler/FirePHPHandler.php
+++ b/src/Monolog/Handler/FirePHPHandler.php
@@ -155,9 +155,12 @@ class FirePHPHandler extends AbstractProcessingHandler
      */
     protected function headersAccepted()
     {
-        return !isset($_SERVER['HTTP_USER_AGENT'])
-               || preg_match('{\bFirePHP/\d+\.\d+\b}', $_SERVER['HTTP_USER_AGENT'])
-               || isset($_SERVER['HTTP_X_FIREPHP_VERSION']);
+        if (empty($_SERVER['HTTP_USER_AGENT'])) {
+            return false;
+        }
+
+        return preg_match('{\bFirePHP/\d+\.\d+\b}', $_SERVER['HTTP_USER_AGENT'])
+        || isset($_SERVER['HTTP_X_FIREPHP_VERSION']);
     }
 
     /**