diff --git a/compiler/src/dotty/tools/dotc/transform/ContextFunctionResults.scala b/compiler/src/dotty/tools/dotc/transform/ContextFunctionResults.scala
index c31b2673e04a..1c045288c94a 100644
--- a/compiler/src/dotty/tools/dotc/transform/ContextFunctionResults.scala
+++ b/compiler/src/dotty/tools/dotc/transform/ContextFunctionResults.scala
@@ -101,7 +101,7 @@ object ContextFunctionResults:
   def contextFunctionResultTypeAfter(meth: Symbol, depth: Int)(using Context) =
     def recur(tp: Type, n: Int): Type =
       if n == 0 then tp
-      else tp match
+      else tp.dealias match
         case defn.FunctionTypeOfMethod(mt) => recur(mt.resType, n - 1)
     recur(meth.info.finalResultType, depth)
 
diff --git a/tests/pos/i21433.scala b/tests/pos/i21433.scala
new file mode 100644
index 000000000000..0efc4ac197ae
--- /dev/null
+++ b/tests/pos/i21433.scala
@@ -0,0 +1,6 @@
+trait A[T]:
+  type R = T ?=> Unit
+  def f: R = ()
+
+class B extends A[Int]:
+  override def f: R = ()