diff --git a/app/Models/Asset.php b/app/Models/Asset.php
index 29231b22c876..2cb14308c6fb 100644
--- a/app/Models/Asset.php
+++ b/app/Models/Asset.php
@@ -122,9 +122,9 @@ public function declinedCheckout(User $declinedBy, $signature)
         'assigned_to'   => ['nullable', 'integer', 'required_with:assigned_type'],
         'assigned_type' => ['nullable', 'required_with:assigned_to', 'in:'.User::class.",".Location::class.",".Asset::class],
         'requestable'       => ['nullable', 'boolean'],
-        'assigned_user'     => ['nullable', 'exists:users,id,deleted_at,NULL'],
-        'assigned_location' => ['nullable', 'exists:locations,id,deleted_at,NULL', 'fmcs_location'],
-        'assigned_asset'    => ['nullable', 'exists:assets,id,deleted_at,NULL']
+        'assigned_user'     => ['integer', 'nullable', 'exists:users,id,deleted_at,NULL'],
+        'assigned_location' => ['integer', 'nullable', 'exists:locations,id,deleted_at,NULL', 'fmcs_location'],
+        'assigned_asset'    => ['integer', 'nullable', 'exists:assets,id,deleted_at,NULL']
     ];
 
 
diff --git a/tests/Feature/Assets/Api/StoreAssetTest.php b/tests/Feature/Assets/Api/StoreAssetTest.php
index 7136b546a398..1af3569f75ab 100644
--- a/tests/Feature/Assets/Api/StoreAssetTest.php
+++ b/tests/Feature/Assets/Api/StoreAssetTest.php
@@ -12,6 +12,7 @@
 use App\Models\User;
 use Illuminate\Support\Facades\Crypt;
 use Illuminate\Testing\Fluent\AssertableJson;
+use PHPUnit\Framework\Attributes\DataProvider;
 use Tests\TestCase;
 
 class StoreAssetTest extends TestCase
@@ -572,6 +573,64 @@ public function testAnAssetCanBeCheckedOutToUserOnStore()
         $this->assertTrue($asset->assignedTo->is($userAssigned));
     }
 
+    public static function checkoutTargets()
+    {
+        yield 'Users' => [
+            function () {
+                return [
+                    'key' => 'assigned_user',
+                    'value' => [
+                        User::factory()->create()->id,
+                        User::factory()->create()->id,
+                    ],
+                ];
+            },
+        ];
+
+        yield 'Locations' => [
+            function () {
+                return [
+                    'key' => 'assigned_location',
+                    'value' => [
+                        Location::factory()->create()->id,
+                        Location::factory()->create()->id,
+                    ],
+                ];
+            },
+        ];
+
+        yield 'Assets' => [
+            function () {
+                return [
+                    'key' => 'assigned_asset',
+                    'value' => [
+                        Asset::factory()->create()->id,
+                        Asset::factory()->create()->id,
+                    ],
+                ];
+            },
+        ];
+    }
+
+    /** @link https://app.shortcut.com/grokability/story/29181 */
+    #[DataProvider('checkoutTargets')]
+    public function testAssignedFieldValidationCannotBeArray($data)
+    {
+        ['key' => $key, 'value' => $value] = $data();
+
+        $this->actingAsForApi(User::factory()->createAssets()->create())
+            ->postJson(route('api.assets.store'), [
+                'asset_tag' => '123456',
+                'model_id' => AssetModel::factory()->create()->id,
+                'status_id' => Statuslabel::factory()->readyToDeploy()->create()->id,
+                $key => $value,
+            ])
+            ->assertStatusMessageIs('error')
+            ->assertJson(function (AssertableJson $json) use ($key) {
+                $json->has("messages.{$key}")->etc();
+            });
+    }
+
     public function testAnAssetCanBeCheckedOutToLocationOnStore()
     {
         $model = AssetModel::factory()->create();