diff --git a/vlib/builtin/map_test.v b/vlib/builtin/map_test.v
new file mode 100644
index 0000000000..06cc7ecc42
--- /dev/null
+++ b/vlib/builtin/map_test.v
@@ -0,0 +1,21 @@
+struct A {
+	m map_int
+}
+
+fn (a mut A) set(key string, val int) {
+	a.m[key] = val
+}
+
+fn test_map() {
+	mut m := map[string]int{}
+	m['hi'] = 80
+	assert m['hi'] == 80
+
+	mut a := A{
+		m: new_map(1, sizeof(int))
+	}
+	a.m['one'] = 1
+	a.set('two', 2)
+	assert a.m['one'] == 1
+	assert a.m['two'] == 2
+}