diff --git a/CHANGELOG.md b/CHANGELOG.md
index af281e5..b941daf 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## (unreleased)
 
+Internal:
+
+* explicit syntax tree representation for first-order formulas
+
 ## 0.1.1 (2017-03-06)
 
 Features: