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
@@ -2066,7 +2066,8 @@
                "Overlay dir must be contained in RPath");
         RPath = RPath.slice(OverlayDirLen, RPath.size());
       }
-      writeEntry(path::filename(Entry.VPath), RPath);
+      if (!Entry.IsDirectory)
+        writeEntry(path::filename(Entry.VPath), RPath);
     }
 
     while (!DirStack.empty()) {
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
@@ -2238,3 +2238,39 @@
   EXPECT_TRUE(FS->exists(_g.Path));
   EXPECT_TRUE(FS->exists(_h.Path));
 }
+
+TEST_F(VFSFromYAMLTest, YAMLVFSWriterTestHandleDirs) {
+  ScopedDir TestDirectory("virtual-file-system-test", /*Unique*/ true);
+  ScopedDir _a(TestDirectory + "/a");
+  ScopedDir _b(TestDirectory + "/b");
+  ScopedDir _c(TestDirectory + "/c");
+
+  vfs::YAMLVFSWriter VFSWriter;
+  VFSWriter.addDirectoryMapping(_a.Path, "//root/a");
+  VFSWriter.addDirectoryMapping(_b.Path, "//root/b");
+  VFSWriter.addDirectoryMapping(_c.Path, "//root/c");
+
+  std::string Buffer;
+  raw_string_ostream OS(Buffer);
+  VFSWriter.write(OS);
+  OS.flush();
+
+  // We didn't add a single file - only directories.
+  EXPECT_TRUE(Buffer.find("'type': 'file'") == std::string::npos);
+
+  IntrusiveRefCntPtr<ErrorDummyFileSystem> Lower(new ErrorDummyFileSystem());
+  Lower->addDirectory("//root/a");
+  Lower->addDirectory("//root/b");
+  Lower->addDirectory("//root/c");
+  // canaries
+  Lower->addRegularFile("//root/a/a");
+  Lower->addRegularFile("//root/b/b");
+  Lower->addRegularFile("//root/c/c");
+
+  IntrusiveRefCntPtr<vfs::FileSystem> FS = getFromYAMLRawString(Buffer, Lower);
+  ASSERT_TRUE(FS.get() != nullptr);
+
+  EXPECT_FALSE(FS->exists(_a.Path + "/a"));
+  EXPECT_FALSE(FS->exists(_b.Path + "/b"));
+  EXPECT_FALSE(FS->exists(_c.Path + "/c"));
+}