diff --git a/gn/src/gn/rsp_target_writer.cc b/gn/src/gn/rsp_target_writer.cc
index 6c1c687e99d..097b84b317e 100644
--- a/src/3rdparty/gn/src/gn/rsp_target_writer.cc
+++ b/src/3rdparty/gn/src/gn/rsp_target_writer.cc
@@ -117,8 +117,7 @@ void RspTargetWriter::Run() {
       PathOutput path_output(settings->build_settings()->build_dir(),
                              settings->build_settings()->root_path_utf8(),
                              ESCAPE_NONE);
-      std::vector<SourceFile> object_files;
-      object_files.reserve(target_->sources().size());
+      std::set<SourceFile> object_files;
 
       for (const auto& source : target_->sources()) {
         const char* tool_type = nullptr;
@@ -128,7 +127,7 @@ void RspTargetWriter::Run() {
             other_files.push_back(source);
           continue;  // No output for this source.
         }
-        object_files.push_back(
+        object_files.insert(
             tool_outputs[0].AsSourceFile(settings->build_settings()));
       }
       if (target_->config_values().has_precompiled_headers()) {
@@ -137,7 +136,7 @@ void RspTargetWriter::Run() {
         if (tool_cxx && tool_cxx->precompiled_header_type() == CTool::PCH_MSVC) {
           GetPCHOutputFiles(target_, CTool::kCToolCxx, &tool_outputs);
           if (!tool_outputs.empty())
-            object_files.push_back(
+            object_files.insert(
                 tool_outputs[0].AsSourceFile(settings->build_settings()));
         }
       }