diff --git a/manifest.json b/manifest.json
index 95f6dac84..5aee20eda 100644
--- a/manifest.json
+++ b/manifest.json
@@ -1,6 +1,6 @@
 {
     "variables": {
-        "${LATEST}": "3.342.8"
+        "${LATEST}": "3.342.9"
     },
     "endpoints": "https://raw.githubusercontent.com/aws/aws-sdk-php/${LATEST}/src/data/endpoints.json",
     "services": {
diff --git a/src/Service/Lambda/CHANGELOG.md b/src/Service/Lambda/CHANGELOG.md
index 135ffd3d8..4587a66d1 100644
--- a/src/Service/Lambda/CHANGELOG.md
+++ b/src/Service/Lambda/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## NOT RELEASED
 
+### Added
+
+- AWS api-change: Add Ruby 3.4 (ruby3.4) support to AWS Lambda.
+
 ## 2.9.0
 
 ### Added
diff --git a/src/Service/Lambda/composer.json b/src/Service/Lambda/composer.json
index 03533e105..d984090ea 100644
--- a/src/Service/Lambda/composer.json
+++ b/src/Service/Lambda/composer.json
@@ -28,7 +28,7 @@
     },
     "extra": {
         "branch-alias": {
-            "dev-master": "2.9-dev"
+            "dev-master": "2.10-dev"
         }
     }
 }
diff --git a/src/Service/Lambda/src/Enum/Runtime.php b/src/Service/Lambda/src/Enum/Runtime.php
index 86fc08a7b..b48bc3812 100644
--- a/src/Service/Lambda/src/Enum/Runtime.php
+++ b/src/Service/Lambda/src/Enum/Runtime.php
@@ -44,6 +44,7 @@ final class Runtime
     public const RUBY_2_7 = 'ruby2.7';
     public const RUBY_3_2 = 'ruby3.2';
     public const RUBY_3_3 = 'ruby3.3';
+    public const RUBY_3_4 = 'ruby3.4';
 
     public static function exists(string $value): bool
     {
@@ -88,6 +89,7 @@ public static function exists(string $value): bool
             self::RUBY_2_7 => true,
             self::RUBY_3_2 => true,
             self::RUBY_3_3 => true,
+            self::RUBY_3_4 => true,
         ][$value]);
     }
 }
diff --git a/src/Service/Lambda/src/Exception/InvalidRequestContentException.php b/src/Service/Lambda/src/Exception/InvalidRequestContentException.php
index a46931564..dedf6e8a8 100644
--- a/src/Service/Lambda/src/Exception/InvalidRequestContentException.php
+++ b/src/Service/Lambda/src/Exception/InvalidRequestContentException.php
@@ -6,7 +6,8 @@
 use Symfony\Contracts\HttpClient\ResponseInterface;
 
 /**
- * The request body could not be parsed as JSON.
+ * The request body could not be parsed as JSON, or a request header is invalid. For example, the 'x-amzn-RequestId'
+ * header is not a valid UUID string.
  */
 final class InvalidRequestContentException extends ClientException
 {