diff --git a/CHANGELOG.md b/CHANGELOG.md
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+++ b/CHANGELOG.md
@@ -1,5 +1,22 @@
 # Changelog
 
+## TBD (Tenatively 0.4.1)
+
+Features
+
+- Store parameter objects in such a way that changes to a parameter object do not affect other threads that use the same parameter object.
+
+The specific requirement from R<sup>7</sup>RS is:
+
+> `parameterize` must not change the associated values of any parameters in any thread other than the current thread and threads created inside the `parameterize` body.
+
+- Normalize the result of `string->number` such that bignums are only returned if the result truly is a bignum.
+
+Bug Fixes
+
+- Prevent exception handlers from being accidentally collected when the collector cooperates on behalf of a mutator.
+- Fixed a regression where `string->number` returns `0` on bad input instead of `#f`.
+
 ## 0.4 - March 9, 2017
 
 - Added a new bignum type to support exact integers of practically unlimited size.