Fix #4039
diff --git a/system/libraries/Session/drivers/Session_files_driver.php b/system/libraries/Session/drivers/Session_files_driver.php
index 45da91c..173b437 100644
--- a/system/libraries/Session/drivers/Session_files_driver.php
+++ b/system/libraries/Session/drivers/Session_files_driver.php
@@ -183,6 +183,12 @@
 				return '';
 			}
 		}
+		// We shouldn't need this, but apparently we do ...
+		// See https://github.com/bcit-ci/CodeIgniter/issues/4039
+		elseif ($this->_file_handler === FALSE)
+		{
+			return FALSE;
+		}
 		else
 		{
 			rewind($this->_file_handle);