diff --git a/tests/pos-deep-subtype/9849.scala b/tests/pos-deep-subtype/9849.scala
new file mode 100644
index 000000000000..45f7288b8956
--- /dev/null
+++ b/tests/pos-deep-subtype/9849.scala
@@ -0,0 +1,4 @@
+type *:[A, B] = A match
+  case (B *: x) => A
+  case (x *: y) => x *: (B *: y)
+  case _ => A *: B