diff --git a/tensorflow/lite/testing/BUILD b/tensorflow/lite/testing/BUILD
index a42228313f9..18502b78c48 100644
--- a/tensorflow/lite/testing/BUILD
+++ b/tensorflow/lite/testing/BUILD
@@ -7,7 +7,7 @@ load(
 )
 load("//tensorflow/lite:special_rules.bzl", "tflite_portable_test_suite")
 load("//tensorflow/lite/testing:tflite_model_test.bzl", "tflite_model_test")
-load("//tensorflow:tensorflow.bzl", "tf_py_wrap_cc")
+load("//tensorflow:tensorflow.bzl", "pybind_extension")
 load(
     "//tensorflow:tensorflow.bzl",
     "py_test",  # @unused
@@ -121,8 +121,8 @@ py_library(
     srcs = ["zip_test_utils.py"],
     srcs_version = "PY2AND3",
     deps = [
+        ":_pywrap_string_util",
         ":generate_examples_report",
-        ":string_util_wrapper",
         "//tensorflow:tensorflow_py",
         "//third_party/py/numpy",
     ],
@@ -513,14 +513,19 @@ cc_library(
     ],
 )
 
-tf_py_wrap_cc(
-    name = "string_util_wrapper",
+pybind_extension(
+    name = "_pywrap_string_util",
     srcs = [
-        "string_util.i",
+        "string_util_wrapper.cc",
     ],
+    hdrs = ["string_util.h"],
+    features = ["-use_header_modules"],
+    module_name = "_pywrap_string_util",
     deps = [
         ":string_util_lib",
+        "//tensorflow/python:pybind11_lib",
         "//third_party/python_runtime:headers",
+        "@pybind11",
     ],
 )
 
diff --git a/tensorflow/lite/testing/string_util.i b/tensorflow/lite/testing/string_util_wrapper.cc
similarity index 56%
rename from tensorflow/lite/testing/string_util.i
rename to tensorflow/lite/testing/string_util_wrapper.cc
index 574abb79653..f5b490ab617 100644
--- a/tensorflow/lite/testing/string_util.i
+++ b/tensorflow/lite/testing/string_util_wrapper.cc
@@ -13,19 +13,25 @@ See the License for the specific language governing permissions and
 limitations under the License.
 ==============================================================================*/
 
-%{
-
-#define SWIG_FILE_WITH_INIT
+#include "include/pybind11/pybind11.h"
+#include "include/pybind11/pytypes.h"
 #include "tensorflow/lite/testing/string_util.h"
+#include "tensorflow/python/lib/core/pybind11_lib.h"
 
-%}
+namespace py = pybind11;
 
-namespace tflite {
-namespace testing {
-namespace python {
-
-PyObject* SerializeAsHexString(PyObject* string_tensor);
-
-}  // namespace python
-}  // namespace testing
-}  // namespace tflite
+PYBIND11_MODULE(_pywrap_string_util, m) {
+  m.doc() = R"pbdoc(
+    _pywrap_string_util
+    -----
+  )pbdoc";
+  m.def(
+      "SerializeAsHexString",
+      [](py::handle& string_tensor) {
+        return tensorflow::pyo_or_throw(
+            tflite::testing::python::SerializeAsHexString(string_tensor.ptr()));
+      },
+      R"pbdoc(
+      Serializes TF Lite dynamic buffer format as a HexString.
+    )pbdoc");
+}
diff --git a/tensorflow/lite/testing/zip_test_utils.py b/tensorflow/lite/testing/zip_test_utils.py
index 3d380ff0385..dcfe77875ff 100644
--- a/tensorflow/lite/testing/zip_test_utils.py
+++ b/tensorflow/lite/testing/zip_test_utils.py
@@ -32,8 +32,8 @@ from six import StringIO
 # pylint: disable=g-import-not-at-top
 import tensorflow as tf
 from google.protobuf import text_format
+from tensorflow.lite.testing import _pywrap_string_util
 from tensorflow.lite.testing import generate_examples_report as report_lib
-from tensorflow.lite.testing import string_util_wrapper
 from tensorflow.python.framework import graph_util as tf_graph_util
 
 # A map from names to functions which make test cases.
@@ -156,7 +156,7 @@ def format_result(t):
     values = ["{:.9f}".format(value) for value in list(t.flatten())]
     return ",".join(values)
   else:
-    return string_util_wrapper.SerializeAsHexString(t.flatten())
+    return _pywrap_string_util.SerializeAsHexString(t.flatten())
 
 
 def write_examples(fp, examples):