diff --git a/src/command_line.cc b/src/command_line.cc
index 66842e675..3c431d41b 100644
--- a/src/command_line.cc
+++ b/src/command_line.cc
@@ -209,6 +209,7 @@ void RunQueryDbThread(const std::string& bin_name) {
   WorkingFiles working_files;
   FileConsumerSharedState file_consumer_shared;
   DiagnosticsEngine diag_engine;
+  diag_engine.Init();
 
   ClangCompleteManager clang_complete(
       &project, &working_files,