diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7492a5d..29eb94e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,10 @@
 # Changelog
 
+## 5.1.1 (2026031800)
+* Fixed PHP 7.3 compatibility issue that broke Moodle 4.0.x servers ([#13](https://github.com/LdesignMedia/moodle-availability_ipaddress/issues/13))
+* Removed typed properties (PHP 7.4+) to support PHP 7.3+
+* Lowered environment.xml PHP requirement from 7.4 to 7.3
+
 ## 5.1.0 (2026030300)
 - Tested and verified on Moodle 5.1
 
@@ -21,5 +26,5 @@
 ## 4.0.2 (2022052800)
 - Fixed the [issue 6](https://github.com/ldesignmediaNL/moodle-availability_ipaddress/issues/6) @[hamzatamyachte](https://github.com/hamzatamyachte)
 
-## 4.0.1 (2022021100)
+## 3.9.0 (2022021100)
 - Thanks for adding ip-range support @[juacas](https://github.com/juacas)