diff --git a/llvm/include/llvm/Support/VirtualFileSystem.h b/llvm/include/llvm/Support/VirtualFileSystem.h
index 3cfb71aa497d7..182a5c1b3cdba 100644
--- a/llvm/include/llvm/Support/VirtualFileSystem.h
+++ b/llvm/include/llvm/Support/VirtualFileSystem.h
@@ -902,6 +902,10 @@ class RedirectingFileSystem : public vfs::FileSystem {
 
   StringRef getExternalContentsPrefixDir() const;
 
+  /// Sets the redirection kind to \c Fallthrough if true or \c RedirectOnly
+  /// otherwise. Will removed in the future, use \c setRedirection instead.
+  void setFallthrough(bool Fallthrough);
+
   void setRedirection(RedirectingFileSystem::RedirectKind Kind);
 
   std::vector<llvm::StringRef> getRoots() const;
diff --git a/llvm/lib/Support/VirtualFileSystem.cpp b/llvm/lib/Support/VirtualFileSystem.cpp
index 8573c3a294e35..49151682624d8 100644
--- a/llvm/lib/Support/VirtualFileSystem.cpp
+++ b/llvm/lib/Support/VirtualFileSystem.cpp
@@ -1363,6 +1363,14 @@ StringRef RedirectingFileSystem::getExternalContentsPrefixDir() const {
   return ExternalContentsPrefixDir;
 }
 
+void RedirectingFileSystem::setFallthrough(bool Fallthrough) {
+  if (Fallthrough) {
+    Redirection = RedirectingFileSystem::RedirectKind::Fallthrough;
+  } else {
+    Redirection = RedirectingFileSystem::RedirectKind::RedirectOnly;
+  }
+}
+
 void RedirectingFileSystem::setRedirection(
     RedirectingFileSystem::RedirectKind Kind) {
   Redirection = Kind;