diff --git a/.release-please-manifest.json b/.release-please-manifest.json
index e82003f..95e4ab6 100644
--- a/.release-please-manifest.json
+++ b/.release-please-manifest.json
@@ -1,3 +1,3 @@
 {
-  ".": "0.11.1"
+  ".": "0.11.2"
 }
\ No newline at end of file
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6db1057..08304d8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,13 @@
 # Changelog
 
+## 0.11.2 (2026-04-18)
+
+Full Changelog: [v0.11.1...v0.11.2](https://github.com/moderation-api/sdk-php/compare/v0.11.1...v0.11.2)
+
+### Bug Fixes
+
+* **client:** resolve serialization issue with unions and enums ([c03ba75](https://github.com/moderation-api/sdk-php/commit/c03ba75a951df565d5b6734f3fd581d356cfccfd))
+
 ## 0.11.1 (2026-04-11)
 
 Full Changelog: [v0.11.0...v0.11.1](https://github.com/moderation-api/sdk-php/compare/v0.11.0...v0.11.1)
diff --git a/README.md b/README.md
index 20f232c..c8e6b8f 100644
--- a/README.md
+++ b/README.md
@@ -11,7 +11,7 @@ The REST API documentation can be found on [docs.moderationapi.com](https://docs
 <!-- x-release-please-start-version -->
 
 ```
-composer require "moderation-api/sdk-php 0.11.1"
+composer require "moderation-api/sdk-php 0.11.2"
 ```
 
 <!-- x-release-please-end -->
diff --git a/src/Core/Attributes/Required.php b/src/Core/Attributes/Required.php
index a1cb601..3e7bd0c 100644
--- a/src/Core/Attributes/Required.php
+++ b/src/Core/Attributes/Required.php
@@ -25,9 +25,6 @@ class Required
 
     public readonly bool $nullable;
 
-    /** @var array<string,Converter> */
-    private static array $enumConverters = [];
-
     /**
      * @param class-string<ConverterSource>|Converter|string|null $type
      * @param class-string<\BackedEnum>|Converter|null            $enum
@@ -52,7 +49,7 @@ public function __construct(
             $type ??= new MapOf($map);
         }
         if (null !== $enum) {
-            $type ??= $enum instanceof Converter ? $enum : self::enumConverter($enum);
+            $type ??= $enum instanceof Converter ? $enum : EnumOf::fromBackedEnum($enum);
         }
 
         $this->apiName = $apiName;
@@ -60,16 +57,4 @@ public function __construct(
         $this->optional = false;
         $this->nullable = $nullable;
     }
-
-    /** @property class-string<\BackedEnum> $enum */
-    private static function enumConverter(string $enum): Converter
-    {
-        if (!isset(self::$enumConverters[$enum])) {
-            // @phpstan-ignore-next-line argument.type
-            $converter = new EnumOf(array_column($enum::cases(), column_key: 'value'));
-            self::$enumConverters[$enum] = $converter;
-        }
-
-        return self::$enumConverters[$enum];
-    }
 }
diff --git a/src/Core/Conversion.php b/src/Core/Conversion.php
index 1b395ef..97f8771 100644
--- a/src/Core/Conversion.php
+++ b/src/Core/Conversion.php
@@ -8,6 +8,7 @@
 use ModerationAPI\Core\Conversion\Contracts\Converter;
 use ModerationAPI\Core\Conversion\Contracts\ConverterSource;
 use ModerationAPI\Core\Conversion\DumpState;
+use ModerationAPI\Core\Conversion\EnumOf;
 
 /**
  * @internal
@@ -65,6 +66,13 @@ public static function coerce(Converter|ConverterSource|string $target, mixed $v
             return $target->coerce($value, state: $state);
         }
 
+        // BackedEnum class-name targets: wrap in EnumOf so enum values are scored
+        // against the enum's cases. Without this, tryConvert's default case scores
+        // any class-name target as `no`, even when the value is a valid enum member.
+        if (is_a($target, class: \BackedEnum::class, allow_string: true)) {
+            return EnumOf::fromBackedEnum($target)->coerce($value, state: $state);
+        }
+
         return self::tryConvert($target, value: $value, state: $state);
     }
 
@@ -78,6 +86,13 @@ public static function dump(Converter|ConverterSource|string $target, mixed $val
             return $target::converter()->dump($value, state: $state);
         }
 
+        // BackedEnum class-name targets: wrap in EnumOf so enum values are scored
+        // against the enum's cases. Without this, tryConvert's default case scores
+        // any class-name target as `no`, even when the value is a valid enum member.
+        if (is_a($target, class: \BackedEnum::class, allow_string: true)) {
+            return EnumOf::fromBackedEnum($target)->dump($value, state: $state);
+        }
+
         self::tryConvert($target, value: $value, state: $state);
 
         return self::dump_unknown($value, state: $state);
diff --git a/src/Core/Conversion/EnumOf.php b/src/Core/Conversion/EnumOf.php
index 7877eb9..a21c137 100644
--- a/src/Core/Conversion/EnumOf.php
+++ b/src/Core/Conversion/EnumOf.php
@@ -14,6 +14,9 @@ final class EnumOf implements Converter
 {
     private readonly string $type;
 
+    /** @var array<class-string<\BackedEnum>, self> */
+    private static array $cache = [];
+
     /**
      * @param list<bool|float|int|string|null> $members
      */
@@ -26,6 +29,13 @@ public function __construct(private readonly array $members)
         $this->type = $type;
     }
 
+    /** @param class-string<\BackedEnum> $enum */
+    public static function fromBackedEnum(string $enum): self
+    {
+        // @phpstan-ignore-next-line argument.type
+        return self::$cache[$enum] ??= new self(array_column($enum::cases(), column_key: 'value'));
+    }
+
     public function coerce(mixed $value, CoerceState $state): mixed
     {
         $this->tally($value, state: $state);
@@ -42,9 +52,10 @@ public function dump(mixed $value, DumpState $state): mixed
 
     private function tally(mixed $value, CoerceState|DumpState $state): void
     {
-        if (in_array($value, haystack: $this->members, strict: true)) {
+        $needle = $value instanceof \BackedEnum ? $value->value : $value;
+        if (in_array($needle, haystack: $this->members, strict: true)) {
             ++$state->yes;
-        } elseif ($this->type === gettype($value)) {
+        } elseif ($this->type === gettype($needle)) {
             ++$state->maybe;
         } else {
             ++$state->no;
diff --git a/src/Version.php b/src/Version.php
index 8d6abc3..0662ea0 100644
--- a/src/Version.php
+++ b/src/Version.php
@@ -5,5 +5,5 @@
 namespace ModerationAPI;
 
 // x-release-please-start-version
-const VERSION = '0.11.1';
+const VERSION = '0.11.2';
 // x-release-please-end