diff --git a/cmake/pybind11.cmake b/cmake/pybind11.cmake
index 4cad4e8..aa99e6a 100644
--- a/cmake/pybind11.cmake
+++ b/cmake/pybind11.cmake
@@ -8,12 +8,9 @@ function(download_pybind11)
 
   include(FetchContent)
 
-  set(pybind11_URL  "https://github.com/pybind/pybind11/archive/v2.6.0.tar.gz")
-  set(pybind11_HASH "SHA256=90b705137b69ee3b5fc655eaca66d0dc9862ea1759226f7ccd3098425ae69571")
+  set(pybind11_URL  "https://github.com/pybind/pybind11/archive/v2.9.2.tar.gz")
+  set(pybind11_HASH "SHA256=6bd528c4dbe2276635dc787b6b1f2e5316cf6b49ee3e150264e455a0d68d19c1")
 
-  set(double_quotes "\"")
-  set(dollar "\$")
-  set(semicolon "\;")
   FetchContent_Declare(pybind11
     URL               ${pybind11_URL}
     URL_HASH          ${pybind11_HASH}
diff --git a/kaldifeat/python/csrc/feature-fbank.cc b/kaldifeat/python/csrc/feature-fbank.cc
index dcc9b14..6e52f0c 100644
--- a/kaldifeat/python/csrc/feature-fbank.cc
+++ b/kaldifeat/python/csrc/feature-fbank.cc
@@ -53,7 +53,7 @@ static void PybindFbank(py::module &m) {
       .def("dim", &PyClass::Dim)
       .def_property_readonly("options", &PyClass::GetOptions)
       .def("compute_features", &PyClass::ComputeFeatures, py::arg("wave"),
-           py::arg("vtln_warp"))
+           py::arg("vtln_warp"), py::call_guard<py::gil_scoped_release>())
       .def(py::pickle(
           [](const PyClass &self) -> py::dict {
             return AsDict(self.GetOptions());
diff --git a/kaldifeat/python/csrc/feature-mfcc.cc b/kaldifeat/python/csrc/feature-mfcc.cc
index 40d330e..fe893cb 100644
--- a/kaldifeat/python/csrc/feature-mfcc.cc
+++ b/kaldifeat/python/csrc/feature-mfcc.cc
@@ -53,7 +53,7 @@ static void PybindMfcc(py::module &m) {
       .def("dim", &PyClass::Dim)
       .def_property_readonly("options", &PyClass::GetOptions)
       .def("compute_features", &PyClass::ComputeFeatures, py::arg("wave"),
-           py::arg("vtln_warp"))
+           py::arg("vtln_warp"), py::call_guard<py::gil_scoped_release>())
       .def(py::pickle(
           [](const PyClass &self) -> py::dict {
             return AsDict(self.GetOptions());
diff --git a/kaldifeat/python/csrc/feature-plp.cc b/kaldifeat/python/csrc/feature-plp.cc
index abc5595..364ef93 100644
--- a/kaldifeat/python/csrc/feature-plp.cc
+++ b/kaldifeat/python/csrc/feature-plp.cc
@@ -56,7 +56,7 @@ static void PybindPlp(py::module &m) {
       .def("dim", &PyClass::Dim)
       .def_property_readonly("options", &PyClass::GetOptions)
       .def("compute_features", &PyClass::ComputeFeatures, py::arg("wave"),
-           py::arg("vtln_warp"))
+           py::arg("vtln_warp"), py::call_guard<py::gil_scoped_release>())
       .def(py::pickle(
           [](const PyClass &self) -> py::dict {
             return AsDict(self.GetOptions());
diff --git a/kaldifeat/python/csrc/feature-spectrogram.cc b/kaldifeat/python/csrc/feature-spectrogram.cc
index 62aa909..24b156b 100644
--- a/kaldifeat/python/csrc/feature-spectrogram.cc
+++ b/kaldifeat/python/csrc/feature-spectrogram.cc
@@ -53,7 +53,7 @@ static void PybindSpectrogram(py::module &m) {
       .def("dim", &PyClass::Dim)
       .def_property_readonly("options", &PyClass::GetOptions)
       .def("compute_features", &PyClass::ComputeFeatures, py::arg("wave"),
-           py::arg("vtln_warp"))
+           py::arg("vtln_warp"), py::call_guard<py::gil_scoped_release>())
       .def(py::pickle(
           [](const PyClass &self) -> py::dict {
             return AsDict(self.GetOptions());