diff --git a/lang/main.c b/lang/main.c
index cfff5bc..30afff6 100644
--- a/lang/main.c
+++ b/lang/main.c
@@ -8,9 +8,9 @@
 static void test_number(void) {
 	struct object *numA = number_create(5);
 	struct object *numB = number_create(3);
-	struct object *args[] = {numB};
+	struct object *args[] = {numB, NULL};
 	dispatch_call(numA, "Add", 1, &args[0]);
-	struct object *numC = args[0];
+	struct object *numC = args[1];
 	printf("numC value is %i\n", number_value(numC));
 	printf("numA is %p\n", (void *)numA);
 	printf("numB is %p\n", (void *)numB);
diff --git a/lang/number.c b/lang/number.c
index 2bce2de..b1ba118 100644
--- a/lang/number.c
+++ b/lang/number.c
@@ -46,7 +46,7 @@
 	struct number *numA = (struct number *)obj;
 	struct number *numB = (struct number *)args[0];
 	int added = numA->value + numB->value;
-	args[0] = number_create(added);
+	args[1] = number_create(added);
 }
 
 static struct object_call calls[] = {