diff --git a/CHANGELOG.md b/CHANGELOG.md
index b39b96e..6b56743 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,12 @@ A version's heading reads `## <version> — Unreleased` until the release is pre
 the release date. The release workflow refuses a tag whose section still says `Unreleased`, and the
 section is the GitHub release's notes.
 
+## 2.4.0 — Unreleased
+
+### Changed
+
+- Packages: the public surface is checked against 2.3.1's, so nothing 2.3.1 ships is removed or changed in 2.4.0.
+
 ## 2.3.1 — 2026-10-31
 
 ### Changed
diff --git a/Directory.Build.props b/Directory.Build.props
index 7333e24..69c73cc 100644
--- a/Directory.Build.props
+++ b/Directory.Build.props
@@ -1,6 +1,6 @@
 <Project>
     <PropertyGroup>
-        <Version>2.3.1</Version>
+        <Version>2.4.0</Version>
         <Authors>CaffeinatedCoder</Authors>
         <Copyright>Copyright (c) 2026 CaffeinatedCoder</Copyright>
         <PackageLicenseExpression>MIT</PackageLicenseExpression>
@@ -42,7 +42,7 @@
     -->
     <PropertyGroup>
         <EnablePackageValidation>true</EnablePackageValidation>
-        <PackageValidationBaselineVersion>2.3.0</PackageValidationBaselineVersion>
+        <PackageValidationBaselineVersion>2.3.1</PackageValidationBaselineVersion>
     </PropertyGroup>
 
     <!-- Provenance: a consumer stepping into this code gets the exact source it is running. -->