diff --git a/compiler/src/dotty/tools/dotc/core/SymDenotations.scala b/compiler/src/dotty/tools/dotc/core/SymDenotations.scala
index 0f94d52f5be9..beeaa2ee922e 100644
--- a/compiler/src/dotty/tools/dotc/core/SymDenotations.scala
+++ b/compiler/src/dotty/tools/dotc/core/SymDenotations.scala
@@ -2226,13 +2226,12 @@ object SymDenotations {
             def computeApplied = {
               btrCache(tp) = NoPrefix
               val baseTp =
-                if (tycon.typeSymbol eq symbol) tp
-                else (tycon.typeParams: @unchecked) match {
+                if (tycon.typeSymbol eq symbol) && !tycon.isLambdaSub then tp
+                else (tycon.typeParams: @unchecked) match
                   case LambdaParam(_, _) :: _ =>
                     recur(tp.superType)
                   case tparams: List[Symbol @unchecked] =>
                     recur(tycon).substApprox(tparams, args)
-                }
               record(tp, baseTp)
               baseTp
             }
diff --git a/tests/pos/argDenot-alpakka.min.scala b/tests/pos/argDenot-alpakka.min.scala
new file mode 100644
index 000000000000..0e509be59cfd
--- /dev/null
+++ b/tests/pos/argDenot-alpakka.min.scala
@@ -0,0 +1,9 @@
+import scala.annotation.unchecked.uncheckedVariance as uV
+
+trait Test:
+  def test[S] =
+    val a: (([O] =>> Foo[O, S]) @uV)[Int] = ???
+    a.m()
+
+class Foo[X, Y]:
+  def m(): Y = ???
diff --git a/tests/pos/argDenot-alpakka.scala b/tests/pos/argDenot-alpakka.scala
new file mode 100644
index 000000000000..41d6ad52ac97
--- /dev/null
+++ b/tests/pos/argDenot-alpakka.scala
@@ -0,0 +1,21 @@
+import scala.annotation.unchecked.uncheckedVariance as uV
+
+trait Test:
+  def split[I, M](in: Flow[I, Byte, M]): SubFlow[Byte, M, in.Repr]
+  def test =
+    split(new Flow[Int, Byte, Unit])
+      .via[Char]
+      .merge
+      .filter()
+
+trait FlowOps[+Out, +Mat]:
+  type Repr[+O] <: FlowOps[O, Mat] { type Repr[+O] = FlowOps.this.Repr[O] }
+  def via[O]:   Repr[O]   = ???
+  def filter(): Repr[Out] = ???
+
+class Flow[-In, +Out, +Mat] extends FlowOps[Out, Mat]:
+  type Repr[+O] = Flow[In @uV, O, Mat @uV]
+
+class SubFlow[+Out, +Mat, +F[+_]] extends FlowOps[Out, Mat]:
+  type Repr[+O] = SubFlow[O, Mat @uV, F @uV]
+  def merge: F[Out] = ???