diff --git a/imperative/python/src/tensor.cpp b/imperative/python/src/tensor.cpp
index e8484d9a..276280f4 100644
--- a/imperative/python/src/tensor.cpp
+++ b/imperative/python/src/tensor.cpp
@@ -240,10 +240,10 @@ TensorWrapper::TensorWrapper(PyObject* args, PyObject* kwargs) {
                     pyf = cpp_apply_const_with_tracing;
                 }
 
-                auto ret = py::reinterpret_steal<py::object>(
-                        PyObject_Call(pyf, tup.ptr(), nullptr));
-                auto py_ret = py::reinterpret_borrow<py::list>(ret);
-                if (auto* t = try_cast(py_ret[0].ptr())) {
+                auto py_ret = PyObject_Call(pyf, tup.ptr(), nullptr);
+                if (!py_ret) throw py::error_already_set();
+                auto py_list = py::reinterpret_steal<py::list>(py_ret);
+                if (auto* t = try_cast(py_list[0].ptr())) {
                     m_tensor = t->m_tensor;
                 }
                 return;
@@ -389,6 +389,7 @@ PyObject* TensorWrapper::device() {
 PyObject* TensorWrapper::numpy() {
     if (m_tensor->m_trace_info.compiled_info != nullptr) {
         PyObject* np_val = PyObject_CallMethod(m_tensor->m_trace_info.compiled_info, "numpy", nullptr);
+        if (!np_val) throw py::error_already_set();
         if (np_val == Py_None) {
             throw TraceReadError("value of this tensor is not read in trace");
         }
@@ -478,6 +479,7 @@ PyObject* TensorWrapper::detach() {
 PyObject* TensorWrapper::_dev_tensor(){
     if (m_tensor->m_trace_info.compiled_info != nullptr) {
         auto *dev_tensor = PyObject_CallMethod(m_tensor->m_trace_info.compiled_info, "_dev_tensor", nullptr);
+        if (!dev_tensor) throw py::error_already_set();
         if (dev_tensor == Py_None) {
             throw TraceReadError("raw data of this tensor is not read in trace");
         }
diff --git a/imperative/python/src/trace.cpp b/imperative/python/src/trace.cpp
index 3a477e24..9571c5cd 100644
--- a/imperative/python/src/trace.cpp
+++ b/imperative/python/src/trace.cpp
@@ -31,9 +31,7 @@ apply_result_t apply_trace(ApplyContext& ctx) {
         }
         py::object ret = py::reinterpret_steal<py::object>(
                 PyObject_Call(cpp_apply_backward_varnode, args.ptr(), nullptr));
-        if (!ret) {
-            throw py::value_error("invalid py object call");
-        }
+        if (!ret) throw py::error_already_set();
 
         // assumption: python function always returns PyList
         auto tup = py::reinterpret_borrow<py::list>(ret);
@@ -58,8 +56,9 @@ apply_result_t apply_trace(ApplyContext& ctx) {
     for (size_t i = 0; i < ctx.nargs; i++) {
         args[i + 1] = TensorWrapper::make(ctx.args[i]->shared_from_this());
     }
-    auto ret = py::reinterpret_steal<py::object>(
-            PyObject_Call(pyf, args.ptr(), nullptr));
+    auto pyout = PyObject_Call(pyf, args.ptr(), nullptr);
+    if (!pyout) throw py::error_already_set();
+    auto ret = py::reinterpret_steal<py::object>(pyout);
 
     // assumption: python function always returns PyList
     auto tup = py::reinterpret_borrow<py::list>(ret);