diff --git a/tensorflow/lite/toco/python/toco_python_api.cc b/tensorflow/lite/toco/python/toco_python_api.cc
index 3f3d301a40d..0f21d0854ae 100644
--- a/tensorflow/lite/toco/python/toco_python_api.cc
+++ b/tensorflow/lite/toco/python/toco_python_api.cc
@@ -47,9 +47,9 @@ namespace toco {
 
 void PopulateConversionLogHelper(const toco::ModelFlags& model_flags,
                                  toco::TocoFlags* toco_flags,
-                                 const string& input_contents_txt,
-                                 const string& output_file_contents_txt,
-                                 const string& error_message,
+                                 const std::string& input_contents_txt,
+                                 const std::string& output_file_contents_txt,
+                                 const std::string& error_message,
                                  GraphVizDumpOptions* dump_options) {
   // Make sure the graphviz file will be dumped under the same folder.
   dump_options->dump_graphviz = toco_flags->conversion_summary_dir();
@@ -167,7 +167,7 @@ PyObject* TocoConvert(PyObject* model_flags_proto_txt_raw,
     dump_options.dump_graphviz_video = toco_flags.dump_graphviz_include_video();
   }
 
-  string output_file_contents_txt;
+  std::string output_file_contents_txt;
   tensorflow::Status status;
   int64 arithmetic_ops_count;
 
@@ -221,7 +221,7 @@ PyObject* TocoGetPotentiallySupportedOps() {
   std::vector<std::string> supported_ops = toco::GetPotentiallySupportedOps();
   PyObject* list = PyList_New(supported_ops.size());
   for (size_t i = 0; i < supported_ops.size(); ++i) {
-    const string& op = supported_ops[i];
+    const std::string& op = supported_ops[i];
     PyObject* op_dict = PyDict_New();
     PyDict_SetItemString(op_dict, "op", PyUnicode_FromString(op.c_str()));
     PyList_SetItem(list, i, op_dict);