diff --git a/resources/lang/en/validation.php b/resources/lang/en/validation.php
index 41d01a6e3b3..98a420e0c72 100644
--- a/resources/lang/en/validation.php
+++ b/resources/lang/en/validation.php
@@ -154,6 +154,7 @@
     |
     */
 
+    'arr_fieldtype' => 'This is invalid.',
     'code_fieldtype_rulers' => 'This is invalid.',
     'date_fieldtype_date_required' => 'Date is required.',
     'date_fieldtype_end_date_invalid' => 'Not a valid end date.',
diff --git a/src/Fieldtypes/Arr.php b/src/Fieldtypes/Arr.php
index 6ec5314463a..97474c3d0f4 100644
--- a/src/Fieldtypes/Arr.php
+++ b/src/Fieldtypes/Arr.php
@@ -2,6 +2,7 @@
 
 namespace Statamic\Fieldtypes;
 
+use Closure;
 use Statamic\Facades\GraphQL;
 use Statamic\Fields\Fieldtype;
 use Statamic\GraphQL\Types\ArrayType;
@@ -81,4 +82,23 @@ public function toGqlType()
     {
         return GraphQL::type(ArrayType::NAME);
     }
+
+    public function rules(): array
+    {
+        if ($this->isKeyed()) {
+            return [];
+        }
+
+        return [function ($handle, $value, Closure $fail) {
+            $values = collect($value);
+
+            if ($values->has('null')) {
+                $fail('statamic::validation.arr_fieldtype')->translate();
+            }
+
+            if ($values->count() !== $values->reject(fn ($v) => is_null($v))->count()) {
+                $fail('statamic::validation.arr_fieldtype')->translate();
+            }
+        }];
+    }
 }