diff --git a/History.md b/History.md
index 49cd41e59..802744c0d 100644
--- a/History.md
+++ b/History.md
@@ -13,6 +13,8 @@ This document maintains a list of changes to Slate with each new version. Until
 
 - **Transforms are no longer exposed on `State` or `Node`.** The transforms API has been completely refactored to be built up of "operations" for collaborative editing support. As part of this refactor, the transforms are now only available via the `state.transform()` API, and aren't exposed on the `State` or `Node` objects as they were before.
 
+- **`Transform` objects are now mutable.** Previously `Transform` was an Immutable.js `Record`, but now it is a simple constructor. This is because transforms are inherently mutating their representation of a state, but this decision is [up for discussion](https://github.com/ianstormtaylor/slate/issues/328).
+
 - **The selection can now be "unset".** Previously, a selection could never be in an "unset" state where the `anchorKey` or `focusKey` was null. This is no longer technically true, although this shouldn't really affect anyone in practice.