diff --git a/src/Manifest/ManifestManager/Options/OutTable/ManifestOptions.php b/src/Manifest/ManifestManager/Options/OutTable/ManifestOptions.php
index 820f18e..80c3757 100644
--- a/src/Manifest/ManifestManager/Options/OutTable/ManifestOptions.php
+++ b/src/Manifest/ManifestManager/Options/OutTable/ManifestOptions.php
@@ -43,6 +43,8 @@ class ManifestOptions
 
     private ?array $tableMetadata = null;
 
+    private ?array $legacyPrimaryKeys = null;
+
     private static function getLegacySerializer(): Serializer
     {
         $normalizer = new ObjectNormalizer(
@@ -78,6 +80,9 @@ private static function getNewNativeTypesSerializer(): Serializer
     public function toArray(bool $legacy = true): array
     {
         $serializer = $legacy ? self::getLegacySerializer() : self::getNewNativeTypesSerializer();
+        if ($this->getLegacyPrimaryKeys() !== null) {
+            $serializer = self::getLegacySerializer();
+        }
 
         return (array) $serializer->normalize($this, null, [AbstractObjectNormalizer::SKIP_NULL_VALUES => true]);
     }
@@ -381,4 +386,15 @@ public function setDeleteWhereOperator(?string $deleteWhereOperator): ManifestOp
         $this->deleteWhereOperator = $deleteWhereOperator;
         return $this;
     }
+
+    public function setLegacyPrimaryKeys(array $primaryKey): ManifestOptions
+    {
+        $this->legacyPrimaryKeys = $primaryKey;
+        return $this;
+    }
+
+    public function getLegacyPrimaryKeys(): ?array
+    {
+        return $this->legacyPrimaryKeys;
+    }
 }
diff --git a/src/Manifest/ManifestManager/Options/OutTable/Serializer/LegacyManifestNormalizer.php b/src/Manifest/ManifestManager/Options/OutTable/Serializer/LegacyManifestNormalizer.php
index f52b85e..b283c84 100644
--- a/src/Manifest/ManifestManager/Options/OutTable/Serializer/LegacyManifestNormalizer.php
+++ b/src/Manifest/ManifestManager/Options/OutTable/Serializer/LegacyManifestNormalizer.php
@@ -19,7 +19,11 @@ public function normalize($object, ?string $format = null, array $context = []):
         /** @var ManifestOptions $object */
         $this->normalizeBasicProperties($object, $data);
         $this->normalizeTableMetadata($object, $data);
-        $this->normalizeSchema($object, $data);
+        if ($object->getLegacyPrimaryKeys() !== null) {
+            $data['primary_key'] = $object->getLegacyPrimaryKeys();
+        } else {
+            $this->normalizeSchema($object, $data);
+        }
 
         return $data;
     }
@@ -119,7 +123,7 @@ public function denormalize($data, string $type, ?string $format = null, array $
         $metadataBackend = $this->setTableMetadata($manifestOptions, $data);
 
         if (isset($data['primary_key']) && !isset($data['columns'])) {
-            throw new OptionsValidationException('Columns must be specified when primary key is specified.');
+            $manifestOptions->setLegacyPrimaryKeys($data['primary_key']);
         }
 
         if (isset($data['columns'])) {
diff --git a/tests/Manifest/ManifestManagerTest.php b/tests/Manifest/ManifestManagerTest.php
index 37cdd56..a079f56 100644
--- a/tests/Manifest/ManifestManagerTest.php
+++ b/tests/Manifest/ManifestManagerTest.php
@@ -150,10 +150,21 @@ public function testManifestWithOnlyPrimaryKeysSpecified(): void
     {
         $manager = new ManifestManager(__DIR__ . '/fixtures/manifest-data-dir');
 
-        $this->expectException(OptionsValidationException::class);
-        $this->expectExceptionMessage('Columns must be specified when primary key is specified.');
+        $expectedManifest = [
+            'destination' => 'destination-table',
+            'primary_key' => [
+                'id',
+                'number',
+            ],
+        ];
+
+        $this->assertSame($expectedManifest, $manager->getTableManifest('onlyPrimaryKeys.csv')->toArray());
 
-        $manager->getTableManifest('onlyPrimaryKeys.csv');
+        // Test that toArray(legacy: false) force fallbacks to the same result
+        $this->assertSame(
+            $expectedManifest,
+            $manager->getTableManifest('onlyPrimaryKeys.csv')->toArray(false),
+        );
     }
 
     public function testNonexistentManifestReturnsEmptyArray(): void