diff --git a/clang/test/VFS/relative-path-errors.c b/clang/test/VFS/relative-path-errors.c
new file mode 100644
--- /dev/null
+++ b/clang/test/VFS/relative-path-errors.c
@@ -0,0 +1,8 @@
+// RUN: mkdir -p %t
+// RUN: cd %t
+// RUN: echo '{"roots": [],"version": 0}' > %t.yaml
+// RUN: cp %s main.c
+// RUN: not %clang_cc1 -ivfsoverlay %t.yaml main.c 2>&1 | FileCheck %s
+
+// CHECK: {{^}}main.c:8:1: error:
+foobarbaz
diff --git a/llvm/lib/Support/VirtualFileSystem.cpp b/llvm/lib/Support/VirtualFileSystem.cpp
--- a/llvm/lib/Support/VirtualFileSystem.cpp
+++ b/llvm/lib/Support/VirtualFileSystem.cpp
@@ -2003,14 +2003,14 @@
 } // namespace
 
 ErrorOr<std::unique_ptr<File>>
-RedirectingFileSystem::openFileForRead(const Twine &Path_) {
-  SmallString<256> Path;
-  Path_.toVector(Path);
+RedirectingFileSystem::openFileForRead(const Twine &Path) {
+  SmallString<256> CanonicalPath;
+  Path.toVector(CanonicalPath);
 
-  if (std::error_code EC = makeCanonical(Path))
+  if (std::error_code EC = makeCanonical(CanonicalPath))
     return EC;
 
-  ErrorOr<RedirectingFileSystem::LookupResult> Result = lookupPath(Path);
+  ErrorOr<RedirectingFileSystem::LookupResult> Result = lookupPath(CanonicalPath);
   if (!Result) {
     if (shouldFallBackToExternalFS(Result.getError()))
       return ExternalFS->openFileForRead(Path);
@@ -2036,7 +2036,7 @@
 
   // FIXME: Update the status with the name and VFSMapped.
   Status S = getRedirectedFileStatus(
-      Path, RE->useExternalName(UseExternalNames), *ExternalStatus);
+      CanonicalPath, RE->useExternalName(UseExternalNames), *ExternalStatus);
   return std::unique_ptr<File>(
       std::make_unique<FileWithFixedStatus>(std::move(*ExternalFile), S));
 }
diff --git a/llvm/unittests/Support/VirtualFileSystemTest.cpp b/llvm/unittests/Support/VirtualFileSystemTest.cpp
--- a/llvm/unittests/Support/VirtualFileSystemTest.cpp
+++ b/llvm/unittests/Support/VirtualFileSystemTest.cpp
@@ -1607,6 +1607,26 @@
   EXPECT_EQ(0, NumDiagnostics);
 }
 
+TEST_F(VFSFromYAMLTest, RelativePathFallthrough) {
+  IntrusiveRefCntPtr<vfs::InMemoryFileSystem> BaseFS =
+      new vfs::InMemoryFileSystem;
+  BaseFS->addFile("//root/foo/a", 0, MemoryBuffer::getMemBuffer("contents of a"));
+  ASSERT_FALSE(BaseFS->setCurrentWorkingDirectory("//root/foo"));
+  auto RemappedFS = vfs::RedirectingFileSystem::create(
+      {}, /*UseExternalNames=*/false, *BaseFS);
+
+  auto OpenedF = RemappedFS->openFileForRead("a");
+  ASSERT_FALSE(OpenedF.getError());
+  llvm::ErrorOr<std::string> Name = (*OpenedF)->getName();
+  ASSERT_FALSE(Name.getError());
+  auto OpenedS = (*OpenedF)->status();
+  ASSERT_FALSE(OpenedS.getError());
+  EXPECT_EQ("a", Name.get());
+  EXPECT_EQ("a", OpenedS->getName());
+  EXPECT_FALSE(OpenedS->IsVFSMapped);
+  EXPECT_EQ(0, NumDiagnostics);
+}
+
 TEST_F(VFSFromYAMLTest, CaseInsensitive) {
   IntrusiveRefCntPtr<DummyFileSystem> Lower(new DummyFileSystem());
   Lower->addRegularFile("//root/foo/bar/a");