diff --git a/compiler/src/dotty/tools/dotc/transform/TypeTestsCasts.scala b/compiler/src/dotty/tools/dotc/transform/TypeTestsCasts.scala
index 3763af243881..0a6b774b83dd 100644
--- a/compiler/src/dotty/tools/dotc/transform/TypeTestsCasts.scala
+++ b/compiler/src/dotty/tools/dotc/transform/TypeTestsCasts.scala
@@ -151,6 +151,7 @@ object TypeTestsCasts {
             // always false test warnings are emitted elsewhere
             X.classSymbol.exists && P.classSymbol.exists &&
               !X.classSymbol.asClass.mayHaveCommonChild(P.classSymbol.asClass)
+            || X.classSymbol.isOneOf(FinalOrSealed)
             || typeArgsTrivial(X, tpe)
             ||| i"its type arguments can't be determined from $X"
         }
diff --git a/tests/pos/16899.scala b/tests/pos/16899.scala
new file mode 100644
index 000000000000..61d1b7dd404b
--- /dev/null
+++ b/tests/pos/16899.scala
@@ -0,0 +1,5 @@
+sealed trait Unset
+
+def foo(v: Unset|Option[Int]): Unit = v match
+  case v: Unset => ()
+  case v: Option[Int] => ()
\ No newline at end of file