diff --git a/bindings/python/src/expose-qpobject.hpp b/bindings/python/src/expose-qpobject.hpp
index 84237b640..288c1a7d2 100644
--- a/bindings/python/src/expose-qpobject.hpp
+++ b/bindings/python/src/expose-qpobject.hpp
@@ -58,9 +58,9 @@ exposeQpObjectDense(nanobind::module_ m)
   //   .def_rw("run_time", &RuizEquilibration<T>::sym);
 
   ::nanobind::class_<dense::QP<T>>(m, "QP")
-    .def(::nanobind::init<i64,
-                          i64,
-                          i64,
+    .def(::nanobind::init<isize,
+                          isize,
+                          isize,
                           bool,
                           proxsuite::proxqp::HessianType,
                           proxsuite::proxqp::DenseBackend>(),
@@ -243,7 +243,7 @@ exposeQpObjectSparse(nanobind::module_ m)
 {
 
   ::nanobind::class_<sparse::QP<T, I>>(m, "QP")
-    .def(::nanobind::init<i64, i64, i64>(),
+    .def(::nanobind::init<isize, isize, isize>(),
          nanobind::arg("n") = 0,
          nanobind::arg("n_eq") = 0,
          nanobind::arg("n_in") = 0,
diff --git a/bindings/python/src/expose-qpvector.hpp b/bindings/python/src/expose-qpvector.hpp
index 1b077a4af..0530ac41a 100644
--- a/bindings/python/src/expose-qpvector.hpp
+++ b/bindings/python/src/expose-qpvector.hpp
@@ -21,7 +21,7 @@ exposeQPVectorDense(nanobind::module_ m)
 
   ::nanobind::class_<dense::BatchQP<T>>(m, "BatchQP")
     .def(
-      ::nanobind::init<u64>(),
+      ::nanobind::init<size_t>(),
       nanobind::arg("batch_size") = 0,
       "Default constructor using the BatchSize of qp models to store.") // constructor
     .def("init_qp_in_place",
@@ -51,7 +51,7 @@ exposeQPVectorSparse(nanobind::module_ m)
 
   ::nanobind::class_<sparse::BatchQP<T, I>>(m, "BatchQP")
     .def(
-      ::nanobind::init<u64>(),
+      ::nanobind::init<long unsigned int>(),
       nanobind::arg("batch_size") = 0,
       "Default constructor using the BatchSize of qp models to store.") // constructor
     .def("init_qp_in_place",
diff --git a/bindings/python/src/expose-results.hpp b/bindings/python/src/expose-results.hpp
index f4bd8c492..bab63daba 100644
--- a/bindings/python/src/expose-results.hpp
+++ b/bindings/python/src/expose-results.hpp
@@ -60,7 +60,7 @@ exposeResults(nanobind::module_ m)
             "find_H_minimal_eigenvalue.");
 
   ::nanobind::class_<Results<T>>(m, "Results")
-    .def(::nanobind::init<i64, i64, i64>(),
+    .def(::nanobind::init<isize, isize, isize>(),
          nanobind::arg("n") = 0,
          nanobind::arg("n_eq") = 0,
          nanobind::arg("n_in") = 0,