diff --git a/src/compiler/scala/tools/nsc/transform/ExtensionMethods.scala b/src/compiler/scala/tools/nsc/transform/ExtensionMethods.scala
index 39e16c3f58b4..5318524870ef 100644
--- a/src/compiler/scala/tools/nsc/transform/ExtensionMethods.scala
+++ b/src/compiler/scala/tools/nsc/transform/ExtensionMethods.scala
@@ -144,6 +144,7 @@ abstract class ExtensionMethods extends Transform with TypingTransformers {
              wrap over other value classes anyway.
             checkNonCyclic(currentOwner.pos, Set(), currentOwner) */
             extensionDefs(currentOwner.companionModule) = new mutable.ListBuffer[Tree]
+            currentOwner.primaryConstructor.makeNotPrivate(NoSymbol)
             super.transform(tree)
           } else if (currentOwner.isStaticOwner) {
             super.transform(tree)
diff --git a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
index 969bb8acebae..5cea250eec35 100644
--- a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
@@ -1686,8 +1686,6 @@ abstract class RefChecks extends InfoTransform with scala.reflect.internal.trans
             val bridges = addVarargBridges(currentOwner)
             checkAllOverrides(currentOwner)
             checkAnyValSubclass(currentOwner)
-            if (currentOwner.isDerivedValueClass)
-              currentOwner.primaryConstructor makeNotPrivate NoSymbol // SI-6601, must be done *after* pickler!
             if (bridges.nonEmpty) deriveTemplate(tree)(_ ::: bridges) else tree
 
           case dc@TypeTreeWithDeferredRefCheck() => abort("adapt should have turned dc: TypeTreeWithDeferredRefCheck into tpt: TypeTree, with tpt.original == dc")
diff --git a/test/files/neg/t6601.check b/test/files/neg/t6601.check
deleted file mode 100644
index 1410e1b11a79..000000000000
--- a/test/files/neg/t6601.check
+++ /dev/null
@@ -1,4 +0,0 @@
-AccessPrivateConstructor_2.scala:2: error: constructor PrivateConstructor in class PrivateConstructor cannot be accessed in class AccessPrivateConstructor
-  new PrivateConstructor("") // Scalac should forbid accessing to the private constructor!
-  ^
-one error found
diff --git a/test/files/neg/t6601/AccessPrivateConstructor_2.scala b/test/files/neg/t6601/AccessPrivateConstructor_2.scala
deleted file mode 100644
index 816bc10d7945..000000000000
--- a/test/files/neg/t6601/AccessPrivateConstructor_2.scala
+++ /dev/null
@@ -1,3 +0,0 @@
-class AccessPrivateConstructor {
-  new PrivateConstructor("") // Scalac should forbid accessing to the private constructor!
-}
diff --git a/test/files/neg/t6601/PrivateConstructor_1.scala b/test/files/neg/t6601/PrivateConstructor_1.scala
deleted file mode 100644
index f09d7ad06825..000000000000
--- a/test/files/neg/t6601/PrivateConstructor_1.scala
+++ /dev/null
@@ -1 +0,0 @@
-class PrivateConstructor private(val s: String) extends AnyVal