diff --git a/compiler/src/dotty/tools/dotc/core/TypeComparer.scala b/compiler/src/dotty/tools/dotc/core/TypeComparer.scala
index 1a1efb3ad082..5120237c954c 100644
--- a/compiler/src/dotty/tools/dotc/core/TypeComparer.scala
+++ b/compiler/src/dotty/tools/dotc/core/TypeComparer.scala
@@ -1575,7 +1575,7 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
    *  Note: It would be legal to do the lifting also if M does not contain opaque types,
    *  but in this case the retries in tryLiftedToThis would be redundant.
    */
-  private def liftToThis(tp: Type): Type = {
+  def liftToThis(tp: Type): Type = {
 
     def findEnclosingThis(moduleClass: Symbol, from: Symbol): Type =
       if ((from.owner eq moduleClass) && from.isPackageObject && from.is(Opaque)) from.thisType
diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index 3d3c0b18292a..4d04bad05cdb 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -712,6 +712,16 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
         typedSelectWithAdapt(tree, pt, qual)
       else EmptyTree
 
+    def tryLiftToThis() =
+      val wtp = qual.tpe.widen
+      val liftedTp = comparing(_.liftToThis(wtp))
+      if liftedTp ne wtp then
+        val qual1 = qual.cast(liftedTp)
+        val tree1 = cpy.Select(tree0)(qual1, selName)
+        val rawType1 = selectionType(tree1, qual1)
+        tryType(tree1, qual1, rawType1)
+      else EmptyTree
+
     def trySmallGenericTuple(tree: untpd.Select, qual: Tree, withCast: Boolean) =
       if qual.tpe.isSmallGenericTuple then
         if withCast then
@@ -761,6 +771,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
     tryType(tree, qual, rawType)
       .orElse(trySimplifyApply())
       .orElse(tryInstantiateTypeVar())
+      .orElse(tryLiftToThis())
       .orElse(trySmallGenericTuple(tree, qual, withCast = true))
       .orElse(tryExt(tree, qual))
       .orElse(tryGadt(tree))
diff --git a/tests/pos/i19609.orig.scala b/tests/pos/i19609.orig.scala
new file mode 100644
index 000000000000..62622075dbed
--- /dev/null
+++ b/tests/pos/i19609.orig.scala
@@ -0,0 +1,12 @@
+object o {
+  opaque type T = String
+
+  summon[o.T =:= T]      // OK
+  summon[o.T =:= String] // OK
+
+  def test1(t: T): Int =
+    t.length // OK
+
+  def test2(t: o.T): Int =
+    t.length // Error: value length is not a member of Playground.o.T
+}
diff --git a/tests/pos/i19609.scala b/tests/pos/i19609.scala
new file mode 100644
index 000000000000..0879fa16c7cf
--- /dev/null
+++ b/tests/pos/i19609.scala
@@ -0,0 +1,24 @@
+object o { u =>
+  opaque type T = String
+
+  def st = summon[String =:= T]
+  def su = summon[String =:= u.T]
+  def so = summon[String =:= o.T]
+
+  def ts = summon[T =:= String]
+  def tu = summon[T =:= u.T]
+  def to = summon[T =:= o.T]
+
+  def us = summon[u.T =:= String]
+  def ut = summon[u.T =:= T]
+  def uo = summon[u.T =:= o.T]
+
+  def os = summon[o.T =:= String]
+  def ot = summon[o.T =:= T]
+  def ou = summon[o.T =:= u.T]
+
+  def ms(x: String): Int = x.length // ok
+  def mt(x:      T): Int = x.length // ok
+  def mu(x:    u.T): Int = x.length // ok
+  def mo(x:    o.T): Int = x.length // was: error: value length is not a member of o.T
+}