diff --git a/candle-pyo3/src/lib.rs b/candle-pyo3/src/lib.rs
index c81cc713..6e206688 100644
--- a/candle-pyo3/src/lib.rs
+++ b/candle-pyo3/src/lib.rs
@@ -11,12 +11,9 @@ pub fn wrap_err(err: ::candle::Error) -> PyErr {
 }
 
 #[derive(Clone)]
-#[pyclass(name = "Tensor")]
+#[pyclass(name = "Tensor", unsendable)]
 struct PyTensor(Tensor);
 
-unsafe impl Send for PyTensor {}
-unsafe impl Sync for PyTensor {}
-
 impl std::ops::Deref for PyTensor {
     type Target = Tensor;