diff --git a/vm/src/stdlib/io.rs b/vm/src/stdlib/io.rs
index 43d496905..f58d55868 100644
--- a/vm/src/stdlib/io.rs
+++ b/vm/src/stdlib/io.rs
@@ -9,7 +9,7 @@ use std::io::SeekFrom;
 use num_traits::ToPrimitive;
 
 use super::os;
-use crate::function::{OptionalArg, PyFuncArgs};
+use crate::function::{OptionalArg, OptionalOption, PyFuncArgs};
 use crate::obj::objbytearray::PyByteArray;
 use crate::obj::objbytes;
 use crate::obj::objbytes::PyBytes;
@@ -21,11 +21,8 @@ use crate::pyobject::TypeProtocol;
 use crate::pyobject::{BufferProtocol, Either, PyObjectRef, PyRef, PyResult, PyValue};
 use crate::vm::VirtualMachine;
 
-fn byte_count(bytes: OptionalArg<Option<PyObjectRef>>) -> i64 {
-    match bytes {
-        OptionalArg::Present(Some(ref int)) => objint::get_value(int).to_i64().unwrap(),
-        _ => (-1 as i64),
-    }
+fn byte_count(bytes: OptionalOption<i64>) -> i64 {
+    bytes.flat_option().unwrap_or(-1 as i64)
 }
 
 #[derive(Debug)]
@@ -134,7 +131,7 @@ impl PyStringIORef {
     //Read k bytes from the object and return.
     //If k is undefined || k == -1, then we read all bytes until the end of the file.
     //This also increments the stream position by the value of k
-    fn read(self, bytes: OptionalArg<Option<PyObjectRef>>, vm: &VirtualMachine) -> PyResult {
+    fn read(self, bytes: OptionalOption<i64>, vm: &VirtualMachine) -> PyResult {
         let data = match self.buffer.borrow_mut().read(byte_count(bytes)) {
             Some(value) => value,
             None => Vec::new(),
@@ -193,7 +190,7 @@ impl PyBytesIORef {
     //Takes an integer k (bytes) and returns them from the underlying buffer
     //If k is undefined || k == -1, then we read all bytes until the end of the file.
     //This also increments the stream position by the value of k
-    fn read(self, bytes: OptionalArg<Option<PyObjectRef>>, vm: &VirtualMachine) -> PyResult {
+    fn read(self, bytes: OptionalOption<i64>, vm: &VirtualMachine) -> PyResult {
         match self.buffer.borrow_mut().read(byte_count(bytes)) {
             Some(value) => Ok(vm.ctx.new_bytes(value)),
             None => Err(vm.new_value_error("Error Retrieving Value".to_string())),
diff --git a/vm/src/stdlib/os.rs b/vm/src/stdlib/os.rs
index fa0b7c2f1..6ec90715c 100644
--- a/vm/src/stdlib/os.rs
+++ b/vm/src/stdlib/os.rs
@@ -334,17 +334,17 @@ fn os_error(message: OptionalArg<PyStringRef>, vm: &VirtualMachine) -> PyResult
     Err(vm.new_os_error(msg))
 }
 
-fn os_fsync(fd: PyIntRef, vm: &VirtualMachine) -> PyResult<()> {
-    let file = rust_file(fd.as_bigint().to_i64().unwrap());
+fn os_fsync(fd: i64, vm: &VirtualMachine) -> PyResult<()> {
+    let file = rust_file(fd);
     file.sync_all().map_err(|err| convert_io_error(vm, err))?;
     // Avoid closing the fd
     raw_file_number(file);
     Ok(())
 }
 
-fn os_read(fd: PyIntRef, n: PyIntRef, vm: &VirtualMachine) -> PyResult {
-    let mut buffer = vec![0u8; n.as_bigint().to_usize().unwrap()];
-    let mut file = rust_file(fd.as_bigint().to_i64().unwrap());
+fn os_read(fd: i64, n: usize, vm: &VirtualMachine) -> PyResult {
+    let mut buffer = vec![0u8; n];
+    let mut file = rust_file(fd);
     file.read_exact(&mut buffer)
         .map_err(|err| convert_io_error(vm, err))?;
 
@@ -353,8 +353,8 @@ fn os_read(fd: PyIntRef, n: PyIntRef, vm: &VirtualMachine) -> PyResult {
     Ok(vm.ctx.new_bytes(buffer))
 }
 
-fn os_write(fd: PyIntRef, data: PyBytesRef, vm: &VirtualMachine) -> PyResult {
-    let mut file = rust_file(fd.as_bigint().to_i64().unwrap());
+fn os_write(fd: i64, data: PyBytesRef, vm: &VirtualMachine) -> PyResult {
+    let mut file = rust_file(fd);
     let written = file.write(&data).map_err(|err| convert_io_error(vm, err))?;
 
     // Avoid closing the fd