diff --git a/src/Monolog/Handler/StreamHandler.php b/src/Monolog/Handler/StreamHandler.php
index 7c0dfd22b..b52607d2e 100644
--- a/src/Monolog/Handler/StreamHandler.php
+++ b/src/Monolog/Handler/StreamHandler.php
@@ -106,7 +106,8 @@ protected function write(array $record)
             restore_error_handler();
             if (!is_resource($this->stream)) {
                 $this->stream = null;
-                throw new \UnexpectedValueException(sprintf('The stream or file "%s" could not be opened: '.$this->errorMessage, $this->url));
+
+                throw new \UnexpectedValueException(sprintf('The stream or file "%s" could not be opened in append mode: '.$this->errorMessage, $this->url));
             }
         }