diff --git a/clang-tools-extra/clangd/ClangdLSPServer.cpp b/clang-tools-extra/clangd/ClangdLSPServer.cpp
--- a/clang-tools-extra/clangd/ClangdLSPServer.cpp
+++ b/clang-tools-extra/clangd/ClangdLSPServer.cpp
@@ -794,7 +794,8 @@
 void ClangdLSPServer::onPrepareRename(const TextDocumentPositionParams &Params,
                                       Callback<llvm::Optional<Range>> Reply) {
   Server->prepareRename(
-      Params.textDocument.uri.file(), Params.position, Opts.Rename,
+      Params.textDocument.uri.file(), Params.position, /*NewName*/ llvm::None,
+      Opts.Rename,
       [Reply = std::move(Reply)](llvm::Expected<RenameResult> Result) mutable {
         if (!Result)
           return Reply(Result.takeError());
diff --git a/clang-tools-extra/clangd/ClangdServer.h b/clang-tools-extra/clangd/ClangdServer.h
--- a/clang-tools-extra/clangd/ClangdServer.h
+++ b/clang-tools-extra/clangd/ClangdServer.h
@@ -273,7 +273,10 @@
                     StringRef TriggerText, Callback<std::vector<TextEdit>> CB);
 
   /// Test the validity of a rename operation.
+  ///
+  /// If NewName is provided, it peforms a name validation.
   void prepareRename(PathRef File, Position Pos,
+                     llvm::Optional<std::string> NewName,
                      const RenameOptions &RenameOpts,
                      Callback<RenameResult> CB);
 
diff --git a/clang-tools-extra/clangd/ClangdServer.cpp b/clang-tools-extra/clangd/ClangdServer.cpp
--- a/clang-tools-extra/clangd/ClangdServer.cpp
+++ b/clang-tools-extra/clangd/ClangdServer.cpp
@@ -399,9 +399,11 @@
 }
 
 void ClangdServer::prepareRename(PathRef File, Position Pos,
+                                 llvm::Optional<std::string> NewName,
                                  const RenameOptions &RenameOpts,
                                  Callback<RenameResult> CB) {
-  auto Action = [Pos, File = File.str(), CB = std::move(CB), RenameOpts,
+  auto Action = [Pos, File = File.str(), CB = std::move(CB),
+                 NewName = std::move(NewName), RenameOpts,
                  this](llvm::Expected<InputsAndAST> InpAST) mutable {
     if (!InpAST)
       return CB(InpAST.takeError());
@@ -413,7 +415,7 @@
     //    the cost, thus the result may be incomplete as it only contains
     //    main-file occurrences;
     auto Results = clangd::rename(
-        {Pos, /*NewName=*/"__clangd_rename_dummy", InpAST->AST, File,
+        {Pos, NewName.getValueOr("__clangd_rename_dummy"), InpAST->AST, File,
          RenameOpts.AllowCrossFile ? nullptr : Index, RenameOpts});
     if (!Results) {
       // LSP says to return null on failure, but that will result in a generic
diff --git a/clang-tools-extra/clangd/unittests/RenameTests.cpp b/clang-tools-extra/clangd/unittests/RenameTests.cpp
--- a/clang-tools-extra/clangd/unittests/RenameTests.cpp
+++ b/clang-tools-extra/clangd/unittests/RenameTests.cpp
@@ -730,8 +730,8 @@
   runAddDocument(Server, FooHPath, FooH.code());
   runAddDocument(Server, FooCCPath, FooCC.code());
 
-  auto Results =
-      runPrepareRename(Server, FooCCPath, FooCC.point(), {/*CrossFile=*/true});
+  auto Results = runPrepareRename(Server, FooCCPath, FooCC.point(),
+                                  /*NewName=*/llvm::None, {/*CrossFile=*/true});
   // verify that for multi-file rename, we only return main-file occurrences.
   ASSERT_TRUE(bool(Results)) << Results.takeError();
   // We don't know the result is complete in prepareRename (passing a nullptr
@@ -740,9 +740,17 @@
   EXPECT_THAT(FooCC.ranges(),
               testing::UnorderedElementsAreArray(Results->LocalChanges));
 
-  // single-file rename on global symbols, we should report an error.
+  // verify name validation.
   Results =
-      runPrepareRename(Server, FooCCPath, FooCC.point(), {/*CrossFile=*/false});
+      runPrepareRename(Server, FooCCPath, FooCC.point(),
+                       /*NewName=*/std::string("int"), {/*CrossFile=*/true});
+  EXPECT_FALSE(Results);
+  EXPECT_THAT(llvm::toString(Results.takeError()),
+              testing::HasSubstr("keyword"));
+
+  // single-file rename on global symbols, we should report an error.
+  Results = runPrepareRename(Server, FooCCPath, FooCC.point(),
+                             /*NewName=*/llvm::None, {/*CrossFile=*/false});
   EXPECT_FALSE(Results);
   EXPECT_THAT(llvm::toString(Results.takeError()),
               testing::HasSubstr("is used outside"));
diff --git a/clang-tools-extra/clangd/unittests/SyncAPI.h b/clang-tools-extra/clangd/unittests/SyncAPI.h
--- a/clang-tools-extra/clangd/unittests/SyncAPI.h
+++ b/clang-tools-extra/clangd/unittests/SyncAPI.h
@@ -46,6 +46,7 @@
 
 llvm::Expected<RenameResult>
 runPrepareRename(ClangdServer &Server, PathRef File, Position Pos,
+                 llvm::Optional<std::string> NewName,
                  const clangd::RenameOptions &RenameOpts);
 
 llvm::Expected<tooling::Replacements>
diff --git a/clang-tools-extra/clangd/unittests/SyncAPI.cpp b/clang-tools-extra/clangd/unittests/SyncAPI.cpp
--- a/clang-tools-extra/clangd/unittests/SyncAPI.cpp
+++ b/clang-tools-extra/clangd/unittests/SyncAPI.cpp
@@ -105,11 +105,12 @@
   return std::move(*Result);
 }
 
-llvm::Expected<RenameResult> runPrepareRename(ClangdServer &Server,
-                                              PathRef File, Position Pos,
-                                              const RenameOptions &RenameOpts) {
+llvm::Expected<RenameResult>
+runPrepareRename(ClangdServer &Server, PathRef File, Position Pos,
+                 llvm::Optional<std::string> NewName,
+                 const RenameOptions &RenameOpts) {
   llvm::Optional<llvm::Expected<RenameResult>> Result;
-  Server.prepareRename(File, Pos, RenameOpts, capture(Result));
+  Server.prepareRename(File, Pos, NewName, RenameOpts, capture(Result));
   return std::move(*Result);
 }