diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index f2268003132a..84796120f8a1 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -1155,8 +1155,8 @@ class Typer extends Namer
               case _ =>
                 if (mt.isParamDependent)
                   errorTree(tree,
-                    i"""internal error: cannot turn method type $mt into closure
-                     |because it has internal parameter dependencies""")
+                    i"""cannot turn method type $mt into closure
+                       |because it has internal parameter dependencies""")
                 else if ((tree.tpt `eq` untpd.ContextualEmptyTree) && mt.paramNames.isEmpty)
                   // Note implicitness of function in target type since there are no method parameters that indicate it.
                   TypeTree(defn.FunctionOf(Nil, mt.resType, isContextual = true, isErased = false))
diff --git a/tests/neg/i6391.scala b/tests/neg/i6391.scala
new file mode 100644
index 000000000000..fbe3e770d8ef
--- /dev/null
+++ b/tests/neg/i6391.scala
@@ -0,0 +1,4 @@
+object Test {
+  def foo(x: String, y: x.type): Any = ???
+  val f = foo  // error // error: cannot convert to closure
+}
\ No newline at end of file