diff --git a/HISTORY.md b/HISTORY.md
index 161c2d6e9..2d3ec6926 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -7,6 +7,7 @@
 ### Bug Fixes
 * Fix a bug that can cause unnecessary bg thread to be scheduled(#6104).
 * Fix a bug in which a snapshot read could be affected by a DeleteRange after the snapshot (#6062).
+* Fixed two performance issues related to memtable history trimming. First, a new SuperVersion is now created only if some memtables were actually trimmed. Second, trimming is only scheduled if there is at least one flushed memtable that is kept in memory for the purposes of transaction conflict checking.
 
 ## 6.6.0 (11/25/2019)
 ### Bug Fixes