diff --git a/sherpa-onnx/python/csrc/offline-recognizer.cc b/sherpa-onnx/python/csrc/offline-recognizer.cc
index 5662a9e9..e70ffe66 100644
--- a/sherpa-onnx/python/csrc/offline-recognizer.cc
+++ b/sherpa-onnx/python/csrc/offline-recognizer.cc
@@ -40,7 +40,8 @@ void PybindOfflineRecognizer(py::module *m) {
 
   using PyClass = OfflineRecognizer;
   py::class_<PyClass>(*m, "OfflineRecognizer")
-      .def(py::init<const OfflineRecognizerConfig &>(), py::arg("config"))
+      .def(py::init<const OfflineRecognizerConfig &>(), py::arg("config"),
+           py::call_guard<py::gil_scoped_release>())
       .def(
           "create_stream",
           [](const PyClass &self) { return self.CreateStream(); },
diff --git a/sherpa-onnx/python/csrc/offline-tts.cc b/sherpa-onnx/python/csrc/offline-tts.cc
index 976ca330..d98d40a3 100644
--- a/sherpa-onnx/python/csrc/offline-tts.cc
+++ b/sherpa-onnx/python/csrc/offline-tts.cc
@@ -48,7 +48,8 @@ void PybindOfflineTts(py::module *m) {
 
   using PyClass = OfflineTts;
   py::class_<PyClass>(*m, "OfflineTts")
-      .def(py::init<const OfflineTtsConfig &>(), py::arg("config"))
+      .def(py::init<const OfflineTtsConfig &>(), py::arg("config"),
+           py::call_guard<py::gil_scoped_release>())
       .def_property_readonly("sample_rate", &PyClass::SampleRate)
       .def(
           "generate",
diff --git a/sherpa-onnx/python/csrc/online-recognizer.cc b/sherpa-onnx/python/csrc/online-recognizer.cc
index be68a104..5a2dba09 100644
--- a/sherpa-onnx/python/csrc/online-recognizer.cc
+++ b/sherpa-onnx/python/csrc/online-recognizer.cc
@@ -53,7 +53,8 @@ void PybindOnlineRecognizer(py::module *m) {
 
   using PyClass = OnlineRecognizer;
   py::class_<PyClass>(*m, "OnlineRecognizer")
-      .def(py::init<const OnlineRecognizerConfig &>(), py::arg("config"))
+      .def(py::init<const OnlineRecognizerConfig &>(), py::arg("config"),
+           py::call_guard<py::gil_scoped_release>())
       .def(
           "create_stream",
           [](const PyClass &self) { return self.CreateStream(); },
diff --git a/sherpa-onnx/python/csrc/voice-activity-detector.cc b/sherpa-onnx/python/csrc/voice-activity-detector.cc
index f3e68318..f360c7ec 100644
--- a/sherpa-onnx/python/csrc/voice-activity-detector.cc
+++ b/sherpa-onnx/python/csrc/voice-activity-detector.cc
@@ -24,7 +24,8 @@ void PybindVoiceActivityDetector(py::module *m) {
   using PyClass = VoiceActivityDetector;
   py::class_<PyClass>(*m, "VoiceActivityDetector")
       .def(py::init<const VadModelConfig &, float>(), py::arg("config"),
-           py::arg("buffer_size_in_seconds") = 60)
+           py::arg("buffer_size_in_seconds") = 60,
+           py::call_guard<py::gil_scoped_release>())
       .def(
           "accept_waveform",
           [](PyClass &self, const std::vector<float> &samples) {