diff --git a/builtin/array.mbt b/builtin/array.mbt
index 2ce7d666..bf77dbe6 100644
--- a/builtin/array.mbt
+++ b/builtin/array.mbt
@@ -982,3 +982,7 @@ pub fn iter2[A](self : Array[A]) -> Iter2[Int, A] {
     },
   )
 }
+
+pub fn Array::default[T]() -> Array[T] {
+  []
+}
diff --git a/builtin/array_test.mbt b/builtin/array_test.mbt
index b1afdea0..9c25e395 100644
--- a/builtin/array_test.mbt
+++ b/builtin/array_test.mbt
@@ -566,3 +566,11 @@ test "array_dedup - edge cases" {
   array.dedup()
   inspect!(array, content="[1, 2, 3, 4, 5]")
 }
+
+struct MX {
+  mm_num : Array[Int]
+} derive(Default, ToJson)
+
+test {
+  @json.inspect!(MX::default(), content={ "mm_num": [] })
+}
diff --git a/builtin/builtin.mbti b/builtin/builtin.mbti
index 54fd2a5b..ee9c282a 100644
--- a/builtin/builtin.mbti
+++ b/builtin/builtin.mbti
@@ -55,6 +55,7 @@ impl Array {
   compare[T : Compare + Eq](Self[T], Self[T]) -> Int
   contains[T : Eq](Self[T], T) -> Bool
   dedup[T : Eq](Self[T]) -> Unit
+  default[T]() -> Self[T]
   drain[T](Self[T], Int, Int) -> Self[T]
   each[T](Self[T], (T) -> Unit) -> Unit
   eachi[T](Self[T], (Int, T) -> Unit) -> Unit