diff --git a/lib/upgrade.txt b/lib/upgrade.txt
index 5b9369011b4..d7caeca1337 100644
--- a/lib/upgrade.txt
+++ b/lib/upgrade.txt
@@ -1,6 +1,12 @@
 This files describes API changes in core libraries and APIs,
 information provided here is intended especially for developers.
 
+=== 2.5.5 / 2.6.2 / 2.7 ===
+
+* New "Time spent waiting for the database" performance metric displayed along with the
+  other MDL_PERF vars; the change affects both the error logs and the vars displayed in
+  the page footer.
+
 === 2.6 ===
 
 * Use new methods from core_component class instead of get_core_subsystems(), get_plugin_types(),