diff --git a/downloader/src/main/kotlin/vcs/GitWorkingTree.kt b/downloader/src/main/kotlin/vcs/GitWorkingTree.kt
index cc62dfe569b15..33494b522b965 100644
--- a/downloader/src/main/kotlin/vcs/GitWorkingTree.kt
+++ b/downloader/src/main/kotlin/vcs/GitWorkingTree.kt
@@ -50,7 +50,7 @@ private fun findGitOrSubmoduleDir(workingDirOrFile: File): Repository {
     }.getOrThrow()
 }
 
-open class GitWorkingTree(
+internal open class GitWorkingTree(
     workingDir: File,
     vcsType: VcsType,
     private val repositoryUrlPrefixReplacements: Map<String, String> = emptyMap()
diff --git a/downloader/src/main/kotlin/vcs/Mercurial.kt b/downloader/src/main/kotlin/vcs/Mercurial.kt
index e9ea098fadbdd..445e0a39c608b 100644
--- a/downloader/src/main/kotlin/vcs/Mercurial.kt
+++ b/downloader/src/main/kotlin/vcs/Mercurial.kt
@@ -55,7 +55,7 @@ class Mercurial : VersionControlSystem(MercurialCommand) {
 
     override fun getDefaultBranchName(url: String) = "default"
 
-    override fun getWorkingTree(vcsDirectory: File) = MercurialWorkingTree(vcsDirectory, type)
+    override fun getWorkingTree(vcsDirectory: File): WorkingTree = MercurialWorkingTree(vcsDirectory, type)
 
     override fun isApplicableUrlInternal(vcsUrl: String) = ProcessCapture("hg", "identify", vcsUrl).isSuccess
 
diff --git a/downloader/src/main/kotlin/vcs/MercurialWorkingTree.kt b/downloader/src/main/kotlin/vcs/MercurialWorkingTree.kt
index 25dbb7b1012e4..b455d18e13cce 100644
--- a/downloader/src/main/kotlin/vcs/MercurialWorkingTree.kt
+++ b/downloader/src/main/kotlin/vcs/MercurialWorkingTree.kt
@@ -25,7 +25,7 @@ import org.ossreviewtoolkit.downloader.WorkingTree
 import org.ossreviewtoolkit.model.VcsType
 import org.ossreviewtoolkit.utils.common.ProcessCapture
 
-class MercurialWorkingTree(workingDir: File, vcsType: VcsType) : WorkingTree(workingDir, vcsType) {
+internal class MercurialWorkingTree(workingDir: File, vcsType: VcsType) : WorkingTree(workingDir, vcsType) {
     override fun isValid(): Boolean {
         if (!workingDir.isDirectory) return false
 
diff --git a/downloader/src/main/kotlin/vcs/Subversion.kt b/downloader/src/main/kotlin/vcs/Subversion.kt
index 4e91820d14c08..ddc70acd31464 100644
--- a/downloader/src/main/kotlin/vcs/Subversion.kt
+++ b/downloader/src/main/kotlin/vcs/Subversion.kt
@@ -66,7 +66,8 @@ class Subversion : VersionControlSystem() {
 
     override fun getDefaultBranchName(url: String) = "trunk"
 
-    override fun getWorkingTree(vcsDirectory: File) = SubversionWorkingTree(vcsDirectory, type, clientManager)
+    override fun getWorkingTree(vcsDirectory: File): WorkingTree =
+        SubversionWorkingTree(vcsDirectory, type, clientManager)
 
     override fun isApplicableUrlInternal(vcsUrl: String) =
         try {
diff --git a/downloader/src/main/kotlin/vcs/SubversionWorkingTree.kt b/downloader/src/main/kotlin/vcs/SubversionWorkingTree.kt
index 0ceea2908c0a1..a83fc12bf3d91 100644
--- a/downloader/src/main/kotlin/vcs/SubversionWorkingTree.kt
+++ b/downloader/src/main/kotlin/vcs/SubversionWorkingTree.kt
@@ -32,7 +32,7 @@ import org.tmatesoft.svn.core.SVNURL
 import org.tmatesoft.svn.core.wc.SVNClientManager
 import org.tmatesoft.svn.core.wc.SVNRevision
 
-class SubversionWorkingTree(
+internal class SubversionWorkingTree(
     workingDir: File,
     vcsType: VcsType,
     private val clientManager: SVNClientManager