diff --git a/CHANGELOG.md b/CHANGELOG.md
index a40a407..3663615 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,7 @@ Version 1.4.0
 - Fixed __getstate__ method in Device class. (issue [#86](https://github.com/truenas/py-SMART/issues/86)). Thanks @f18m
 - Added DEVELOP.md file to help developers to get started with the project. (MR [#87](https://github.com/truenas/py-SMART/pull/87/files)). Thanks @ssteinerx
 - Fixed listing devices on MACOS (issue [#84](https://github.com/truenas/py-SMART/issues/84)). Thanks @evanrich
+- Fixed get_selftest_result (issue [#88](https://github.com/truenas/py-SMART/issues/88)). Thanks @guanfeix
 - **Breaking changes**
     - **smartctl.all**:
         - Officially removed support for python 3.7.
diff --git a/pySMART/device.py b/pySMART/device.py
index ccd4d32..2359726 100644
--- a/pySMART/device.py
+++ b/pySMART/device.py
@@ -791,7 +791,7 @@ def get_selftest_result(self, output=None):
         if (
                 (len(self.tests) != _len) or
                 (
-                    len == maxlog and
+                    _len == maxlog and
                     (
                         _first_entry.type != self.tests[0].type or
                         _first_entry.hours != self.tests[0].hours or