CHANGES.md in json_pure-2.5.0 vs CHANGES.md in json_pure-2.5.1

@@ -1,6 +1,10 @@
 # Changes
 
+## 2020-12-22 (2.5.1)
+
+* Restore the compatibility for constants of JSON class.
+
 ## 2020-12-22 (2.5.0)
 
 * Ready to Ractor-safe at Ruby 3.0.
 
 ## 2020-12-17 (2.4.1)