diff --git a/clang-tools-extra/clangd/index/dex/dexp/Dexp.cpp b/clang-tools-extra/clangd/index/dex/dexp/Dexp.cpp
--- a/clang-tools-extra/clangd/index/dex/dexp/Dexp.cpp
+++ b/clang-tools-extra/clangd/index/dex/dexp/Dexp.cpp
@@ -19,6 +19,7 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/LineEditor/LineEditor.h"
 #include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Path.h"
 #include "llvm/Support/Signals.h"
 
 namespace clang {
@@ -381,6 +382,10 @@
     return -1;
   }
 
+  if (!ProjectRoot.empty() &&
+      !llvm::StringRef(ProjectRoot).endswith(llvm::sys::path::get_separator()))
+    ProjectRoot += llvm::sys::path::get_separator();
+
   std::unique_ptr<SymbolIndex> Index;
   reportTime(RemoteMode ? "Remote index client creation" : "Dex build",
              [&]() { Index = openIndex(IndexLocation); });
diff --git a/clang-tools-extra/clangd/index/remote/Client.cpp b/clang-tools-extra/clangd/index/remote/Client.cpp
--- a/clang-tools-extra/clangd/index/remote/Client.cpp
+++ b/clang-tools-extra/clangd/index/remote/Client.cpp
@@ -76,7 +76,9 @@
       : Stub(remote::SymbolIndex::NewStub(Channel)),
         ProtobufMarshaller(new Marshaller(/*RemoteIndexRoot=*/"",
                                           /*LocalIndexRoot=*/ProjectRoot)),
-        DeadlineWaitingTime(DeadlineTime) {}
+        DeadlineWaitingTime(DeadlineTime) {
+    assert(!ProjectRoot.empty());
+  }
 
   void lookup(const clangd::LookupRequest &Request,
               llvm::function_ref<void(const clangd::Symbol &)> Callback) const {
diff --git a/clang-tools-extra/clangd/tool/ClangdMain.cpp b/clang-tools-extra/clangd/tool/ClangdMain.cpp
--- a/clang-tools-extra/clangd/tool/ClangdMain.cpp
+++ b/clang-tools-extra/clangd/tool/ClangdMain.cpp
@@ -702,6 +702,10 @@
     return 1;
   }
   if (!RemoteIndexAddress.empty()) {
+    if (!ProjectRoot.empty() &&
+        !llvm::StringRef(ProjectRoot)
+             .endswith(llvm::sys::path::get_separator()))
+      ProjectRoot += llvm::sys::path::get_separator();
     if (IndexFile.empty()) {
       log("Connecting to remote index at {0}", RemoteIndexAddress);
       StaticIdx = remote::getClient(RemoteIndexAddress, ProjectRoot);