diff --git a/src/messages/text_document_did_open.cc b/src/messages/text_document_did_open.cc
index a16c0fb7..0bd4f990 100644
--- a/src/messages/text_document_did_open.cc
+++ b/src/messages/text_document_did_open.cc
@@ -14,10 +14,15 @@ struct Ipc_TextDocumentDidOpen
   const static IpcId kIpcId = IpcId::TextDocumentDidOpen;
   struct Params {
     lsTextDocumentItem textDocument;
+
+    // cquery extension
+    // If specified (e.g. ["clang++", "-DM", "a.cc"]), it overrides the project
+    // entry (e.g. loaded from compile_commands.json or .cquery).
+    std::vector<std::string> args;
   };
   Params params;
 };
-MAKE_REFLECT_STRUCT(Ipc_TextDocumentDidOpen::Params, textDocument);
+MAKE_REFLECT_STRUCT(Ipc_TextDocumentDidOpen::Params, textDocument, args);
 MAKE_REFLECT_STRUCT(Ipc_TextDocumentDidOpen, params);
 REGISTER_IPC_MESSAGE(Ipc_TextDocumentDidOpen);
 
@@ -26,15 +31,14 @@ struct TextDocumentDidOpenHandler
   void Run(Ipc_TextDocumentDidOpen* request) override {
     // NOTE: This function blocks code lens. If it starts taking a long time
     // we will need to find a way to unblock the code lens request.
-
+    const auto& params = request->params;
     Timer time;
-    std::string path = request->params.textDocument.uri.GetPath();
+    std::string path = params.textDocument.uri.GetPath();
     if (ShouldIgnoreFileForIndexing(path))
       return;
 
     std::shared_ptr<ICacheManager> cache_manager = ICacheManager::Make(config);
-    WorkingFile* working_file =
-        working_files->OnOpen(request->params.textDocument);
+    WorkingFile* working_file = working_files->OnOpen(params.textDocument);
     optional<std::string> cached_file_contents =
         cache_manager->LoadCachedFileContents(path);
     if (cached_file_contents)
@@ -57,8 +61,9 @@ struct TextDocumentDidOpenHandler
     // Submit new index request.
     const Project::Entry& entry = project->FindCompilationEntryForFile(path);
     QueueManager::instance()->index_request.PushBack(
-        Index_Request(entry.filename, entry.args, true /*is_interactive*/,
-                      request->params.textDocument.text, cache_manager),
+        Index_Request(
+            entry.filename, params.args.size() ? params.args : entry.args,
+            true /*is_interactive*/, params.textDocument.text, cache_manager),
         true /* priority */);
   }
 };