Index: clangd/ClangdLSPServer.h
===================================================================
--- clangd/ClangdLSPServer.h
+++ clangd/ClangdLSPServer.h
@@ -85,7 +85,7 @@
                         Callback<std::vector<Location>>);
   void onReference(const ReferenceParams &, Callback<std::vector<Location>>);
   void onSwitchSourceHeader(const TextDocumentIdentifier &,
-                            Callback<llvm::Optional<std::string>>);
+                            Callback<llvm::Optional<URIForFile>>);
   void onDocumentHighlight(const TextDocumentPositionParams &,
                            Callback<std::vector<DocumentHighlight>>);
   void onFileEvent(const DidChangeWatchedFilesParams &);
Index: clangd/ClangdLSPServer.cpp
===================================================================
--- clangd/ClangdLSPServer.cpp
+++ clangd/ClangdLSPServer.cpp
@@ -825,9 +825,9 @@
 
 void ClangdLSPServer::onSwitchSourceHeader(
     const TextDocumentIdentifier &Params,
-    Callback<llvm::Optional<std::string>> Reply) {
+    Callback<llvm::Optional<URIForFile>> Reply) {
   if (auto Result = Server->switchSourceHeader(Params.uri.file()))
-    Reply(URI::resolvePath(*Result, Params.uri.file()));
+    Reply(URIForFile::canonicalize(*Result, Params.uri.file()));
   else
     Reply(llvm::None);
 }