diff --git a/src/ffi.rs b/src/ffi.rs
index 24c8e9b..4938ed6 100644
--- a/src/ffi.rs
+++ b/src/ffi.rs
@@ -3,7 +3,7 @@ use std::{
     ffi::{c_char, CStr},
     fs::File,
     os::raw::c_void,
-    panic::{catch_unwind, AssertUnwindSafe},
+    panic::{catch_unwind, AssertUnwindSafe}, io::Cursor,
 };
 
 use ark_bn254::{Bn254, Fr};
@@ -28,6 +28,10 @@ pub const ERR_CANT_READ_ZKEY: i32 = 6;
 pub const ERR_CIRCOM_BUILDER: i32 = 7;
 pub const ERR_FAILED_TO_DESERIALIZE_PROOF: i32 = 8;
 pub const ERR_FAILED_TO_DESERIALIZE_INPUTS: i32 = 9;
+pub const ERR_FAILED_TO_VERIFY_PROOF: i32 = 10;
+pub const ERR_GET_PUB_INPUTS: i32 = 11;
+pub const ERR_MAKING_PROOF: i32 = 12;
+pub const ERR_SERIALIZE_PROOF: i32 = 13;
 
 #[derive(Debug, Clone)]
 #[repr(C)]
@@ -150,6 +154,7 @@ pub unsafe extern "C" fn release_circom_compat(ctx_ptr: &mut *mut CircomCompatCt
 }
 
 #[no_mangle]
+// Only use if the buffer was allocated by the ffi
 pub unsafe extern "C" fn release_buffer(buff_ptr: &mut *mut Buffer) {
     if !buff_ptr.is_null() {
         let buff = &mut Box::from_raw(*buff_ptr);
@@ -164,39 +169,6 @@ unsafe fn to_circom(ctx_ptr: *mut CircomCompatCtx) -> *mut CircomBn254 {
     (*ctx_ptr).circom as *mut CircomBn254
 }
 
-/// # Safety
-///
-#[no_mangle]
-#[allow(private_interfaces)]
-pub unsafe extern "C" fn push_input_u256_array(
-    ctx_ptr: *mut CircomCompatCtx,
-    name_ptr: *const c_char,
-    input_ptr: *const u8,
-    len: usize,
-) -> i32 {
-    let result = catch_unwind(AssertUnwindSafe(|| {
-        let name = CStr::from_ptr(name_ptr)
-            .to_str()
-            .map_err(|_| ERR_INPUT_NAME)
-            .unwrap();
-
-        let input = {
-            let slice = std::slice::from_raw_parts(input_ptr, len);
-            slice
-                .chunks(U256::BYTES)
-                .map(|c| U256::try_from_le_slice(c).ok_or(ERR_INVALID_INPUT).unwrap())
-                .collect::<Vec<U256>>()
-        };
-
-        let circom = &mut *to_circom(ctx_ptr);
-        input
-            .iter()
-            .for_each(|c| (*circom.builder).push_input(name, *c));
-    }));
-
-    to_err_code(result)
-}
-
 /// # Safety
 ///
 #[no_mangle]
@@ -212,10 +184,19 @@ pub unsafe extern "C" fn prove_circuit(
         let proving_key = &(*circom.proving_key);
         let rng = &mut (*ctx_ptr).rng;
 
-        let circuit = (*circom.builder).clone().build().unwrap();
+        let circuit = (*circom.builder)
+            .clone()
+            .build()
+            .map_err(|_| ERR_CIRCOM_BUILDER)
+            .unwrap();
 
-        let inputs = circuit.get_public_inputs().unwrap();
-        let proof = GrothBn::prove(&proving_key, circuit, rng).unwrap();
+        let inputs = circuit
+            .get_public_inputs()
+            .ok_or_else(|| ERR_GET_PUB_INPUTS)
+            .unwrap();
+        let proof = GrothBn::prove(&proving_key, circuit, rng)
+            .map_err(|_| ERR_MAKING_PROOF)
+            .unwrap();
 
         let mut proof_bytes = Vec::new();
         proof.serialize_compressed(&mut proof_bytes).unwrap();
@@ -223,6 +204,7 @@ pub unsafe extern "C" fn prove_circuit(
         let mut public_inputs_bytes = Vec::new();
         inputs
             .serialize_compressed(&mut public_inputs_bytes)
+            .map_err(|_| ERR_SERIALIZE_PROOF)
             .unwrap();
 
         // leak the buffers to avoid rust from freeing the pointed to data,
@@ -278,13 +260,46 @@ pub unsafe extern "C" fn verify_circuit(
         let pvk = prepare_verifying_key(&proving_key.vk);
 
         GrothBn::verify_proof(&pvk, &proof, &public_inputs)
-            .map_err(|e| e.to_string())
+            .map_err(|_| ERR_FAILED_TO_VERIFY_PROOF)
             .unwrap();
     }));
 
     to_err_code(result)
 }
 
+/// # Safety
+///
+#[no_mangle]
+#[allow(private_interfaces)]
+pub unsafe extern "C" fn push_input_u256_array(
+    ctx_ptr: *mut CircomCompatCtx,
+    name_ptr: *const c_char,
+    input_ptr: *const u8,
+    len: usize,
+) -> i32 {
+    let result = catch_unwind(AssertUnwindSafe(|| {
+        let name = CStr::from_ptr(name_ptr)
+            .to_str()
+            .map_err(|_| ERR_INPUT_NAME)
+            .unwrap();
+
+        let input = {
+            let slice = std::slice::from_raw_parts(input_ptr, len);
+            slice
+                .chunks(U256::BYTES)
+                .map(|c| U256::try_from_le_slice(c).ok_or(ERR_INVALID_INPUT).unwrap())
+                .collect::<Vec<U256>>()
+        };
+
+        let circom = &mut *to_circom(ctx_ptr);
+        input
+            .iter()
+            .for_each(|c| (*circom.builder).push_input(name, *c));
+    }));
+
+    to_err_code(result)
+}
+
 macro_rules! build_fn
 {
     ($name:tt, $($v:ident: $t:ty),*) => {
@@ -296,7 +311,7 @@ macro_rules! build_fn
             input: $($t),*
         ) -> i32 {
             let result = catch_unwind(AssertUnwindSafe(|| {
-                let name = CStr::from_ptr(name_ptr).to_str().unwrap();
+                let name = CStr::from_ptr(name_ptr).to_str().map_err(|_| ERR_INPUT_NAME).unwrap();
                 let input = U256::from(input);
 
                 let circom = &mut *to_circom(ctx_ptr);
@@ -323,7 +338,7 @@ mod test {
     use super::*;
 
     #[test]
-    fn groth16_proof() {
+    fn proof_verify() {
         let r1cs_path = CString::new("./fixtures/mycircuit.r1cs".as_bytes()).unwrap();
         let wasm_path = CString::new("./fixtures/mycircuit.wasm".as_bytes()).unwrap();