diff --git a/.release-please-manifest.json b/.release-please-manifest.json
index c780d338..00fe239c 100644
--- a/.release-please-manifest.json
+++ b/.release-please-manifest.json
@@ -3,7 +3,7 @@
   "pkgs/dotnet-server-sdk-dynamodb": "4.0.0",
   "pkgs/dotnet-server-sdk-redis": "5.1.0",
   "pkgs/sdk/server": "8.10.3",
-  "pkgs/sdk/client": "5.5.3",
+  "pkgs/sdk/client": "5.5.4",
   "pkgs/telemetry": "1.3.0",
   "pkgs/sdk/server-ai": "0.9.1",
   "pkgs/shared/common": "7.1.1",
diff --git a/pkgs/sdk/client/CHANGELOG.md b/pkgs/sdk/client/CHANGELOG.md
index 56fe9cca..4fb5eafb 100644
--- a/pkgs/sdk/client/CHANGELOG.md
+++ b/pkgs/sdk/client/CHANGELOG.md
@@ -3,6 +3,13 @@
 All notable changes to the LaunchDarkly Client-Side SDK for .NET will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org).
 
+## [5.5.4](https://github.com/launchdarkly/dotnet-core/compare/LaunchDarkly.ClientSdk-v5.5.3...LaunchDarkly.ClientSdk-v5.5.4) (2025-09-29)
+
+
+### Bug Fixes
+
+* Validate string format of SDK key ([#162](https://github.com/launchdarkly/dotnet-core/issues/162)) ([27a26fb](https://github.com/launchdarkly/dotnet-core/commit/27a26fb9e226f7e5208928d9df43fbd6d5a68037))
+
 ## [5.5.3](https://github.com/launchdarkly/dotnet-core/compare/LaunchDarkly.ClientSdk-v5.5.2...LaunchDarkly.ClientSdk-v5.5.3) (2025-09-25)
 
 
diff --git a/pkgs/sdk/client/src/LaunchDarkly.ClientSdk.csproj b/pkgs/sdk/client/src/LaunchDarkly.ClientSdk.csproj
index 50b37a93..3ae874b5 100644
--- a/pkgs/sdk/client/src/LaunchDarkly.ClientSdk.csproj
+++ b/pkgs/sdk/client/src/LaunchDarkly.ClientSdk.csproj
@@ -2,7 +2,7 @@
 
     <PropertyGroup>
         <!--x-release-please-start-version-->
-        <Version>5.5.3</Version>
+        <Version>5.5.4</Version>
         <!--x-release-please-end-->
         <!-- The BUILDFRAMEWORKS variable allows us to override the target frameworks in
              a situation where we need to build only the .NET Standard target and do not