diff --git a/cvode-wrap/src/lib.rs b/cvode-wrap/src/lib.rs
index 1aa421d..e8f3e07 100644
--- a/cvode-wrap/src/lib.rs
+++ b/cvode-wrap/src/lib.rs
@@ -10,10 +10,9 @@ use cvode_5_sys::{
 };
 
 mod nvector;
-use nvector::NVectorSerialHeapAlloced;
+pub use nvector::{NVectorSerial, NVectorSerialHeapAlloced};
 
 pub type Realtype = realtype;
-pub type CVector = cvode::N_Vector;
 
 #[repr(u32)]
 #[derive(Debug)]
@@ -74,15 +73,21 @@ pub enum RhsResult {
     NonRecoverableError(u8),
 }
 
-pub type RhsF<UserData, const N: usize> = fn(t: Realtype, y: &[Realtype; N], ydot: &mut [Realtype; N], user_data: &UserData) -> RhsResult;
+pub type RhsF<UserData, const N: usize> =
+    fn(t: Realtype, y: &[Realtype; N], ydot: &mut [Realtype; N], user_data: &UserData) -> RhsResult;
 
-pub type RhsFCtype<UserData> = extern "C" fn(t: Realtype, y: CVector, ydot: CVector, user_data: *const UserData) -> c_int;
+pub type RhsFCtype<UserData, const N: usize> = extern "C" fn(
+    t: Realtype,
+    y: *const NVectorSerial<N>,
+    ydot: *mut NVectorSerial<N>,
+    user_data: *const UserData,
+) -> c_int;
 
 pub fn wrap_f<UserData, const N: usize>(
     f: RhsF<UserData, N>,
     t: Realtype,
-    y: CVector,
-    ydot: CVector,
+    y: *const NVectorSerial<N>,
+    ydot: *mut NVectorSerial<N>,
     data: &UserData,
 ) -> c_int {
     let y = unsafe { transmute(N_VGetArrayPointer(y as _)) };
@@ -97,12 +102,12 @@ pub fn wrap_f<UserData, const N: usize>(
 
 #[macro_export]
 macro_rules! wrap {
-    ($wrapped_f_name: ident, $f_name: ident, $user_data: ty) => {
+    ($wrapped_f_name: ident, $f_name: ident, $user_data: ty, $problem_size: expr) => {
         extern "C" fn $wrapped_f_name(
             t: Realtype,
-            y: CVector,
-            ydot: CVector,
-            data: *const  $user_data,
+            y: *const NVectorSerial<$problem_size>,
+            ydot: *mut NVectorSerial<$problem_size>,
+            data: *const $user_data,
         ) -> std::os::raw::c_int {
             let data = unsafe { std::mem::transmute(data) };
             wrap_f($f_name, t, y, ydot, data)
@@ -155,7 +160,7 @@ impl<const SIZE: usize> AbsTolerance<SIZE> {
 impl<UserData, const N: usize> Solver<UserData, N> {
     pub fn new(
         method: LinearMultistepMethod,
-        f: RhsFCtype<UserData>,
+        f: RhsFCtype<UserData, N>,
         t0: Realtype,
         y0: &[Realtype; N],
         rtol: Realtype,
@@ -196,7 +201,14 @@ impl<UserData, const N: usize> Solver<UserData, N> {
             user_data,
         };
         {
-            let flag = unsafe { cvode::CVodeInit(mem.as_raw(), Some(std::mem::transmute(f)), t0, res.y0.as_raw() as _) };
+            let flag = unsafe {
+                cvode::CVodeInit(
+                    mem.as_raw(),
+                    Some(std::mem::transmute(f)),
+                    t0,
+                    res.y0.as_raw() as _,
+                )
+            };
             check_flag_is_succes(flag, "CVodeInit")?;
         }
         match &res.atol {
@@ -232,7 +244,11 @@ impl<UserData, const N: usize> Solver<UserData, N> {
         Ok(res)
     }
 
-    pub fn step(&mut self, tout: Realtype, step_kind: StepKind) -> Result<(Realtype, &[Realtype; N])> {
+    pub fn step(
+        &mut self,
+        tout: Realtype,
+        step_kind: StepKind,
+    ) -> Result<(Realtype, &[Realtype; N])> {
         let mut tret = 0.;
         let flag = unsafe {
             cvode::CVode(
@@ -260,12 +276,17 @@ impl<UserData, const N: usize> Drop for Solver<UserData, N> {
 mod tests {
     use super::*;
 
-    fn f(_t: super::Realtype, y: &[Realtype; 2], ydot: &mut [Realtype; 2], _data: &()) -> RhsResult {
+    fn f(
+        _t: super::Realtype,
+        y: &[Realtype; 2],
+        ydot: &mut [Realtype; 2],
+        _data: &(),
+    ) -> RhsResult {
         *ydot = [y[1], -y[0]];
         RhsResult::Ok
     }
 
-    wrap!(wrapped_f, f, ());
+    wrap!(wrapped_f, f, (), 2);
 
     #[test]
     fn create() {
diff --git a/cvode-wrap/src/nvector.rs b/cvode-wrap/src/nvector.rs
index f3e363e..089a631 100644
--- a/cvode-wrap/src/nvector.rs
+++ b/cvode-wrap/src/nvector.rs
@@ -1,23 +1,24 @@
-use std::{convert::TryInto, intrinsics::transmute, ops::Deref, ptr::NonNull};
+use std::{
+    convert::TryInto,
+    intrinsics::transmute,
+    ops::{Deref, DerefMut},
+    ptr::NonNull,
+};
 
 use cvode_5_sys::{cvode::realtype, nvector_serial};
 
-
 #[repr(transparent)]
 #[derive(Debug)]
-pub struct NVectorSerialHeapAlloced<const SIZE: usize> {
-    inner: NonNull<nvector_serial::_generic_N_Vector>,
+pub struct NVectorSerial<const SIZE: usize> {
+    inner: nvector_serial::_generic_N_Vector,
 }
 
-impl<const SIZE: usize> Deref for NVectorSerialHeapAlloced<SIZE> {
-    type Target = nvector_serial::_generic_N_Vector;
-
-    fn deref(&self) -> &Self::Target {
-        unsafe {self.inner.as_ref()}
+impl<const SIZE: usize> NVectorSerial<SIZE> {
+    
+    pub unsafe fn as_raw(&self) -> nvector_serial::N_Vector {
+        std::mem::transmute(&self.inner)
     }
- }
 
-impl<const SIZE: usize> NVectorSerialHeapAlloced<SIZE> {
     pub fn as_slice(&self) -> &[realtype; SIZE] {
         unsafe { transmute(nvector_serial::N_VGetArrayPointer_Serial(self.as_raw())) }
     }
@@ -25,11 +26,33 @@ impl<const SIZE: usize> NVectorSerialHeapAlloced<SIZE> {
     pub fn as_slice_mut(&mut self) -> &mut [realtype; SIZE] {
         unsafe { transmute(nvector_serial::N_VGetArrayPointer_Serial(self.as_raw())) }
     }
+}
 
+#[repr(transparent)]
+#[derive(Debug)]
+pub struct NVectorSerialHeapAlloced<const SIZE: usize> {
+    inner: NonNull<NVectorSerial<SIZE>>,
+}
+
+impl<const SIZE: usize> Deref for NVectorSerialHeapAlloced<SIZE> {
+    type Target = NVectorSerial<SIZE>;
+
+    fn deref(&self) -> &Self::Target {
+        unsafe { self.inner.as_ref() }
+    }
+}
+
+impl<const SIZE: usize> DerefMut for NVectorSerialHeapAlloced<SIZE> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        unsafe { self.inner.as_mut() }
+    }
+}
+
+impl<const SIZE: usize> NVectorSerialHeapAlloced<SIZE> {
     pub fn new() -> Self {
+        let raw_c = unsafe { nvector_serial::N_VNew_Serial(SIZE.try_into().unwrap()) };
         Self {
-            inner: NonNull::new(unsafe { nvector_serial::N_VNew_Serial(SIZE.try_into().unwrap()) })
-                .unwrap(),
+            inner: NonNull::new(raw_c as *mut NVectorSerial<SIZE>).unwrap(),
         }
     }
 
@@ -38,10 +61,6 @@ impl<const SIZE: usize> NVectorSerialHeapAlloced<SIZE> {
         res.as_slice_mut().copy_from_slice(data);
         res
     }
-
-    pub fn as_raw(&self) -> nvector_serial::N_Vector {
-        self.inner.as_ptr()
-    }
 }
 
 impl<const SIZE: usize> Drop for NVectorSerialHeapAlloced<SIZE> {
diff --git a/test-solver/src/main.rs b/test-solver/src/main.rs
index 7dfa0c0..2399681 100644
--- a/test-solver/src/main.rs
+++ b/test-solver/src/main.rs
@@ -7,7 +7,7 @@ fn main() {
         *ydot = [y[1], -y[0] * k];
         RhsResult::Ok
     }
-    wrap!(wrapped_f, f, Realtype);
+    wrap!(wrapped_f, f, Realtype, 2);
     //initialize the solver
     let mut solver = Solver::new(
         LinearMultistepMethod::ADAMS,