diff --git a/CHANGELOG.md b/CHANGELOG.md
index e7a322f8c..90b20041e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,12 @@ You can find and compare releases at the [GitHub release page](https://github.co
 
 ## Unreleased
 
+## v15.9.1
+
+### Fixed
+
+- Allow enum instances in `PhpEnumType::parseValue()` https://github.com/webonyx/graphql-php/pull/1519
+
 ## v15.9.0
 
 ### Added
diff --git a/src/Type/Definition/PhpEnumType.php b/src/Type/Definition/PhpEnumType.php
index fafe27d6c..fa92ae643 100644
--- a/src/Type/Definition/PhpEnumType.php
+++ b/src/Type/Definition/PhpEnumType.php
@@ -47,7 +47,7 @@ public function __construct(string $enum, string $name = null)
 
     public function serialize($value): string
     {
-        if (! is_a($value, $this->enumClass)) {
+        if (! ($value instanceof $this->enumClass)) {
             $notEnum = Utils::printSafe($value);
             throw new SerializationError("Cannot serialize value as enum: {$notEnum}, expected instance of {$this->enumClass}.");
         }
@@ -55,6 +55,16 @@ public function serialize($value): string
         return $value->name;
     }
 
+    public function parseValue($value)
+    {
+        // Can happen when variable values undergo a serialization cycle before execution
+        if ($value instanceof $this->enumClass) {
+            return $value;
+        }
+
+        return parent::parseValue($value);
+    }
+
     /** @param class-string $class */
     protected function baseName(string $class): string
     {
diff --git a/tests/Type/PhpEnumTypeTest.php b/tests/Type/PhpEnumTypeTest.php
index 4545a332f..c9c2b4c97 100644
--- a/tests/Type/PhpEnumTypeTest.php
+++ b/tests/Type/PhpEnumTypeTest.php
@@ -14,6 +14,7 @@
 use GraphQL\Tests\Type\PhpEnumType\PhpEnum;
 use GraphQL\Type\Definition\ObjectType;
 use GraphQL\Type\Definition\PhpEnumType;
+use GraphQL\Type\Definition\ResolveInfo;
 use GraphQL\Type\Definition\Type;
 use GraphQL\Type\Schema;
 use GraphQL\Utils\SchemaPrinter;
@@ -135,6 +136,62 @@ public function testExecutesWithEnumTypeFromPhpEnum(): void
         ], GraphQL::executeQuery($schema, '{ foo(bar: A) }')->toArray());
     }
 
+    public function testAcceptsEnumFromVariableValues(): void
+    {
+        $enumType = new PhpEnumType(PhpEnum::class);
+
+        $schema = null;
+        $schema = new Schema([
+            'query' => new ObjectType([
+                'name' => 'Query',
+                'fields' => [
+                    'foo' => [
+                        'type' => Type::nonNull($enumType),
+                        'args' => [
+                            'bar' => [
+                                'type' => Type::nonNull($enumType),
+                            ],
+                        ],
+                        'resolve' => static function (bool $executeAgain, array $args, $context, ResolveInfo $resolveInfo) use (&$schema): PhpEnum {
+                            $bar = $args['bar'];
+                            assert($bar === PhpEnum::A);
+
+                            if ($executeAgain) {
+                                $executionResult = GraphQL::executeQuery(
+                                    $schema,
+                                    'query ($bar: PhpEnum!) { foo(bar: $bar) }',
+                                    false,
+                                    null,
+                                    $resolveInfo->variableValues
+                                );
+                                self::assertSame([
+                                    'data' => [
+                                        'foo' => 'A',
+                                    ],
+                                ], $executionResult->toArray(DebugFlag::RETHROW_INTERNAL_EXCEPTIONS));
+                            }
+
+                            return $bar;
+                        },
+                    ],
+                ],
+            ]),
+        ]);
+
+        $executionResult = GraphQL::executeQuery(
+            $schema,
+            'query ($bar: PhpEnum!) { foo(bar: $bar) }',
+            true,
+            null,
+            ['bar' => 'A']
+        );
+        self::assertSame([
+            'data' => [
+                'foo' => 'A',
+            ],
+        ], $executionResult->toArray(DebugFlag::RETHROW_INTERNAL_EXCEPTIONS));
+    }
+
     public function testFailsToSerializeNonEnum(): void
     {
         $enumType = new PhpEnumType(PhpEnum::class);