diff --git a/phpseclib/File/ANSI.php b/phpseclib/File/ANSI.php
index 989537be..eb6b8383 100644
--- a/phpseclib/File/ANSI.php
+++ b/phpseclib/File/ANSI.php
@@ -332,6 +332,9 @@ class File_ANSI
                             case preg_match('#\x1B\[(\d+)D#', $this->ansi, $match): // Move cursor left n lines
                                 $this->old_x = $this->x;
                                 $this->x-= $match[1];
+                                if ($this->x < 0) {
+                                    $this->x = 0;
+                                }
                                 break;
                             case preg_match('#\x1B\[(\d+);(\d+)r#', $this->ansi, $match): // Set top and bottom lines of a window
                                 break;