diff --git a/src/autoload.rs b/src/autoload.rs
index 3568a1e17..323f70a7d 100644
--- a/src/autoload.rs
+++ b/src/autoload.rs
@@ -336,7 +336,19 @@ fn test_autoload() {
     }
 
     fn touch_file(path: &wstr) {
-        let fd = wopen_cloexec(path, O_RDWR | O_CREAT, 0o666).unwrap();
+        use nix::sys::stat::Mode;
+
+        let fd = wopen_cloexec(
+            path,
+            O_RDWR | O_CREAT,
+            Mode::S_IRUSR
+                | Mode::S_IWUSR
+                | Mode::S_IRGRP
+                | Mode::S_IWGRP
+                | Mode::S_IROTH
+                | Mode::S_IWOTH,
+        )
+        .unwrap();
         write_loop(&fd, "Hello".as_bytes()).unwrap();
         unsafe { libc::close(fd) };
     }
diff --git a/src/builtins/cd.rs b/src/builtins/cd.rs
index 4bbc7c7e7..ccb461ef7 100644
--- a/src/builtins/cd.rs
+++ b/src/builtins/cd.rs
@@ -9,6 +9,7 @@ use crate::{
 };
 use errno::{self, Errno};
 use libc::{fchdir, EACCES, ELOOP, ENOENT, ENOTDIR, EPERM, O_RDONLY};
+use nix::sys::stat::Mode;
 use std::{os::fd::AsRawFd, sync::Arc};
 
 // The cd builtin. Changes the current directory to the one specified or to $HOME if none is
@@ -86,7 +87,7 @@ pub fn cd(parser: &Parser, streams: &mut IoStreams, args: &mut [&wstr]) -> Optio
 
         errno::set_errno(Errno(0));
 
-        let res = wopen_cloexec(&norm_dir, O_RDONLY, 0)
+        let res = wopen_cloexec(&norm_dir, O_RDONLY, Mode::empty())
             .map(AutoCloseFd::new)
             .map_err(|err| err as i32);
 
diff --git a/src/builtins/source.rs b/src/builtins/source.rs
index 5e9dbf460..f3b6c5e95 100644
--- a/src/builtins/source.rs
+++ b/src/builtins/source.rs
@@ -8,6 +8,7 @@ use crate::{
     reader::reader_read,
 };
 use libc::{c_int, O_RDONLY, S_IFMT, S_IFREG};
+use nix::sys::stat::Mode;
 
 use super::prelude::*;
 
@@ -50,7 +51,7 @@ pub fn source(parser: &Parser, streams: &mut IoStreams, args: &mut [&wstr]) -> O
         func_filename = FilenameRef::new(L!("-").to_owned());
         fd = streams.stdin_fd;
     } else {
-        let Ok(raw_fd) = wopen_cloexec(args[optind], O_RDONLY, 0) else {
+        let Ok(raw_fd) = wopen_cloexec(args[optind], O_RDONLY, Mode::empty()) else {
             let esc = escape(args[optind]);
             streams.err.append(wgettext_fmt!(
                 "%ls: Error encountered while sourcing file '%ls':\n",
diff --git a/src/env_universal_common.rs b/src/env_universal_common.rs
index 875c2b5fe..0ca6f3034 100644
--- a/src/env_universal_common.rs
+++ b/src/env_universal_common.rs
@@ -20,6 +20,7 @@ use crate::wutil::{
 };
 use errno::{errno, Errno};
 use libc::{EINTR, LOCK_EX, O_CREAT, O_RDONLY, O_RDWR};
+use nix::sys::stat::Mode;
 use std::collections::hash_map::Entry;
 use std::collections::HashSet;
 use std::ffi::CString;
@@ -388,7 +389,7 @@ impl EnvUniversal {
             return true;
         }
 
-        let Ok(raw_fd) = open_cloexec(&self.narrow_vars_path, O_RDONLY, 0) else {
+        let Ok(raw_fd) = open_cloexec(&self.narrow_vars_path, O_RDONLY, Mode::empty()) else {
             return false;
         };
 
@@ -441,7 +442,11 @@ impl EnvUniversal {
 
         let mut res_fd = None;
         while res_fd.is_none() {
-            let raw = match wopen_cloexec(&self.vars_path, flags, 0o644) {
+            let raw = match wopen_cloexec(
+                &self.vars_path,
+                flags,
+                Mode::S_IRUSR | Mode::S_IWUSR | Mode::S_IRGRP | Mode::S_IROTH,
+            ) {
                 Ok(raw) => raw,
                 Err(err) => {
                     if err == nix::Error::EINTR {
diff --git a/src/exec.rs b/src/exec.rs
index 9e6633b45..2d7088ebd 100644
--- a/src/exec.rs
+++ b/src/exec.rs
@@ -53,6 +53,7 @@ use libc::{
     c_char, EACCES, ENOENT, ENOEXEC, ENOTDIR, EPIPE, EXIT_FAILURE, EXIT_SUCCESS, O_NOCTTY,
     O_RDONLY, STDERR_FILENO, STDIN_FILENO, STDOUT_FILENO,
 };
+use nix::sys::stat;
 use std::ffi::CStr;
 use std::io::{Read, Write};
 use std::os::fd::{FromRawFd, RawFd};
@@ -366,7 +367,7 @@ pub fn is_thompson_shell_script(path: &CStr) -> bool {
     }
     let e = errno();
     let mut res = false;
-    let fd = open_cloexec(path, O_RDONLY | O_NOCTTY, 0);
+    let fd = open_cloexec(path, O_RDONLY | O_NOCTTY, stat::Mode::empty());
     if let Ok(fd) = fd {
         let mut file = unsafe { std::fs::File::from_raw_fd(fd) };
         let mut buf = [b'\0'; 256];
diff --git a/src/fds.rs b/src/fds.rs
index 8c9761209..eee768e21 100644
--- a/src/fds.rs
+++ b/src/fds.rs
@@ -222,14 +222,17 @@ pub fn set_cloexec(fd: RawFd, should_set: bool /* = true */) -> c_int {
 
 /// Wide character version of open() that also sets the close-on-exec flag (atomically when
 /// possible).
-pub fn wopen_cloexec(pathname: &wstr, flags: i32, mode: libc::c_int) -> nix::Result<RawFd> {
+pub fn wopen_cloexec(
+    pathname: &wstr,
+    flags: i32,
+    mode: nix::sys::stat::Mode,
+) -> nix::Result<RawFd> {
     open_cloexec(wcs2zstring(pathname).as_c_str(), flags, mode)
 }
 
 /// Narrow versions of wopen_cloexec.
-pub fn open_cloexec(path: &CStr, flags: i32, mode: libc::c_int) -> nix::Result<RawFd> {
+pub fn open_cloexec(path: &CStr, flags: i32, mode: nix::sys::stat::Mode) -> nix::Result<RawFd> {
     let flags = unsafe { OFlag::from_bits_unchecked(flags) };
-    let mode = unsafe { nix::sys::stat::Mode::from_bits_unchecked(mode as u32) };
     // Port note: the C++ version of this function had a fallback for platforms where
     // O_CLOEXEC is not supported, using fcntl. In 2023, this is no longer needed.
     let saved_errno = errno();
diff --git a/src/history.rs b/src/history.rs
index 60491fa0e..f764bddc0 100644
--- a/src/history.rs
+++ b/src/history.rs
@@ -36,6 +36,7 @@ use libc::{
     O_RDONLY, O_WRONLY, SEEK_SET,
 };
 use lru::LruCache;
+use nix::sys::stat::Mode;
 use rand::Rng;
 
 use crate::{
@@ -130,7 +131,7 @@ const HISTORY_SAVE_MAX: NonZeroUsize = unsafe { NonZeroUsize::new_unchecked(1024
 const HISTORY_OUTPUT_BUFFER_SIZE: usize = 64 * 1024;
 
 /// The file access mode we use for creating history files
-const HISTORY_FILE_MODE: i32 = 0o600;
+const HISTORY_FILE_MODE: Mode = Mode::S_IRUSR.union(Mode::S_IWUSR);
 
 /// How many times we retry to save
 /// Saving may fail if the file is modified in between our opening
@@ -480,7 +481,7 @@ impl HistoryImpl {
 
         let _profiler = TimeProfiler::new("load_old");
         if let Some(filename) = history_filename(&self.name, L!("")) {
-            let Ok(raw_fd) = wopen_cloexec(&filename, O_RDONLY, 0) else {
+            let Ok(raw_fd) = wopen_cloexec(&filename, O_RDONLY, Mode::empty()) else {
                 return;
             };
 
@@ -697,7 +698,7 @@ impl HistoryImpl {
             // If the open fails, then proceed; this may be because there is no current history
             let mut new_file_id = INVALID_FILE_ID;
 
-            let target_fd_after = wopen_cloexec(&target_name, O_RDONLY, 0)
+            let target_fd_after = wopen_cloexec(&target_name, O_RDONLY, Mode::empty())
                 .map(|raw_fd| unsafe { OwnedFd::from_raw_fd(raw_fd) });
 
             if let Ok(target_fd_after) = target_fd_after.as_ref() {
@@ -814,7 +815,7 @@ impl HistoryImpl {
         // Limit our max tries so we don't do this forever.
         let mut history_fd = None;
         for _i in 0..MAX_SAVE_TRIES {
-            let Ok(fd) = wopen_cloexec(&history_path, O_WRONLY | O_APPEND, 0) else {
+            let Ok(fd) = wopen_cloexec(&history_path, O_WRONLY | O_APPEND, Mode::empty()) else {
                 // can't open, we're hosed
                 break;
             };
@@ -1105,7 +1106,7 @@ impl HistoryImpl {
         old_file.push_utfstr(&self.name);
         old_file.push_str("_history");
 
-        let Ok(src_fd) = wopen_cloexec(&old_file, O_RDONLY, 0) else {
+        let Ok(src_fd) = wopen_cloexec(&old_file, O_RDONLY, Mode::empty()) else {
             return;
         };
 
diff --git a/src/io.rs b/src/io.rs
index 5f3b8caeb..9be8a0683 100644
--- a/src/io.rs
+++ b/src/io.rs
@@ -18,6 +18,7 @@ use crate::wchar::prelude::*;
 use crate::wutil::{perror, perror_io, wdirname, wstat, wwrite_to_fd};
 use errno::Errno;
 use libc::{EAGAIN, EINTR, ENOENT, ENOTDIR, EPIPE, EWOULDBLOCK, O_EXCL, STDOUT_FILENO};
+use nix::sys::stat::Mode;
 use std::cell::{RefCell, UnsafeCell};
 use std::os::fd::RawFd;
 use std::sync::atomic::{AtomicU64, Ordering};
@@ -1006,7 +1007,12 @@ const FILE_ERROR: &wstr = L!("An error occurred while redirecting file '%ls'");
 const NOCLOB_ERROR: &wstr = L!("The file '%ls' already exists");
 
 /// Base open mode to pass to calls to open.
-const OPEN_MASK: libc::c_int = 0o666;
+const OPEN_MASK: Mode = Mode::S_IRUSR
+    .union(Mode::S_IWUSR)
+    .union(Mode::S_IRGRP)
+    .union(Mode::S_IWGRP)
+    .union(Mode::S_IROTH)
+    .union(Mode::S_IWOTH);
 
 /// Provide the fd monitor used for background fillthread operations.
 fn fd_monitor() -> &'static mut FdMonitor {
diff --git a/src/parser.rs b/src/parser.rs
index 1d80eb127..0a29cfaac 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -34,6 +34,7 @@ use crate::wchar::{wstr, WString, L};
 use crate::wutil::{perror, wgettext, wgettext_fmt};
 use libc::c_int;
 use libc::O_RDONLY;
+use nix::sys::stat::Mode;
 use once_cell::sync::Lazy;
 use printf_compat::sprintf;
 use std::cell::{Ref, RefCell, RefMut};
@@ -358,7 +359,11 @@ impl Parser {
             global_event_blocks: AtomicU64::new(0),
         });
 
-        match open_cloexec(CStr::from_bytes_with_nul(b".\0").unwrap(), O_RDONLY, 0) {
+        match open_cloexec(
+            CStr::from_bytes_with_nul(b".\0").unwrap(),
+            O_RDONLY,
+            Mode::empty(),
+        ) {
             Ok(raw_fd) => {
                 result.libdata_mut().cwd_fd = Some(Arc::new(AutoCloseFd::new(raw_fd)));
             }
diff --git a/src/reader.rs b/src/reader.rs
index 68e646531..280ff848e 100644
--- a/src/reader.rs
+++ b/src/reader.rs
@@ -17,6 +17,7 @@ use libc::{
     IXOFF, IXON, ONLCR, OPOST, O_NONBLOCK, O_RDONLY, SIGINT, SIGTTIN, STDIN_FILENO, STDOUT_FILENO,
     S_IFDIR, TCSANOW, VMIN, VQUIT, VSUSP, VTIME, _POSIX_VDISABLE,
 };
+use nix::sys::stat::Mode;
 use once_cell::sync::Lazy;
 use std::cell::UnsafeCell;
 use std::io::BufReader;
@@ -4659,7 +4660,7 @@ impl ReaderData {
                 var.map_or_else(|| L!("~/.bash_history").to_owned(), |var| var.as_string());
             expand_tilde(&mut path, self.vars());
 
-            let Ok(raw_fd) = wopen_cloexec(&path, O_RDONLY, 0) else {
+            let Ok(raw_fd) = wopen_cloexec(&path, O_RDONLY, Mode::empty()) else {
                 return;
             };
 
diff --git a/src/tests/history.rs b/src/tests/history.rs
index c5c038452..0e645715f 100644
--- a/src/tests/history.rs
+++ b/src/tests/history.rs
@@ -8,6 +8,7 @@ use crate::tests::string_escape::ESCAPE_TEST_CHAR;
 use crate::wchar::prelude::*;
 use crate::wcstringutil::{string_prefixes_string, string_prefixes_string_case_insensitive};
 use libc::O_RDONLY;
+use nix::sys::stat::Mode;
 use rand::random;
 use std::collections::VecDeque;
 use std::ffi::CString;
@@ -594,8 +595,9 @@ fn test_history_formats() {
         "echo foo".into(),
     ];
     let test_history_imported_from_bash = History::with_name(L!("bash_import"));
-    let file =
-        AutoCloseFd::new(wopen_cloexec(L!("tests/history_sample_bash"), O_RDONLY, 0).unwrap());
+    let file = AutoCloseFd::new(
+        wopen_cloexec(L!("tests/history_sample_bash"), O_RDONLY, Mode::empty()).unwrap(),
+    );
     test_history_imported_from_bash.populate_from_bash(BufReader::new(file));
     assert_eq!(test_history_imported_from_bash.get_history(), expected);
     test_history_imported_from_bash.clear();