diff --git a/vm/src/builtins/mod.rs b/vm/src/builtins/mod.rs
index f52fe3da3..21fa922ad 100644
--- a/vm/src/builtins/mod.rs
+++ b/vm/src/builtins/mod.rs
@@ -15,7 +15,7 @@ pub(crate) mod complex;
 pub use complex::PyComplex;
 pub(crate) mod coroutine;
 pub use coroutine::PyCoroutine;
-pub(crate) mod dict;
+pub mod dict;
 pub use dict::{PyDict, PyDictRef};
 pub(crate) mod enumerate;
 pub use enumerate::PyEnumerate;
diff --git a/vm/src/stdlib/os.rs b/vm/src/stdlib/os.rs
index 0009fb43a..83ffe8217 100644
--- a/vm/src/stdlib/os.rs
+++ b/vm/src/stdlib/os.rs
@@ -1994,12 +1994,10 @@ pub(crate) use _os::os_open as open;
 mod posix {
     use super::*;
 
-    use crate::builtins::dict::PyMapping;
     use crate::builtins::list::PyListRef;
-    use crate::PyIterable;
     use bitflags::bitflags;
-    use nix::errno::{errno, Errno};
     use nix::unistd::{self, Gid, Pid, Uid};
+    #[allow(unused_imports)] // TODO: use will be unnecessary in edition 2021
     use std::convert::TryFrom;
     use std::os::unix::io::RawFd;
 
@@ -2112,6 +2110,7 @@ mod posix {
     #[cfg(any(target_os = "macos", target_os = "ios"))]
     fn getgroups_impl() -> nix::Result<Vec<Gid>> {
         use libc::{c_int, gid_t};
+        use nix::errno::{errno, Errno};
         use std::ptr;
         let ret = unsafe { libc::getgroups(0, ptr::null_mut()) };
         let mut groups = Vec::<Gid>::with_capacity(Errno::result(ret)? as usize);
@@ -2742,7 +2741,7 @@ mod posix {
     // cfg from nix
     #[cfg(not(any(target_os = "ios", target_os = "macos", target_os = "redox")))]
     #[pyfunction]
-    fn setgroups(group_ids: PyIterable<u32>, vm: &VirtualMachine) -> PyResult<()> {
+    fn setgroups(group_ids: crate::PyIterable<u32>, vm: &VirtualMachine) -> PyResult<()> {
         let gids = group_ids
             .iter(vm)?
             .map(|entry| match entry {
@@ -2789,13 +2788,13 @@ mod posix {
         #[pyarg(positional)]
         path: PyPathLike,
         #[pyarg(positional)]
-        args: PyIterable<PyPathLike>,
+        args: crate::PyIterable<PyPathLike>,
         #[pyarg(positional)]
-        env: PyMapping,
+        env: crate::builtins::dict::PyMapping,
         #[pyarg(named, default)]
-        file_actions: Option<PyIterable<PyTupleRef>>,
+        file_actions: Option<crate::PyIterable<PyTupleRef>>,
         #[pyarg(named, default)]
-        setsigdef: Option<PyIterable<i32>>,
+        setsigdef: Option<crate::PyIterable<i32>>,
     }
 
     #[cfg(any(target_os = "linux", target_os = "freebsd", target_os = "macos"))]
@@ -2980,7 +2979,7 @@ mod posix {
     fn waitpid(pid: libc::pid_t, opt: i32, vm: &VirtualMachine) -> PyResult<(libc::pid_t, i32)> {
         let mut status = 0;
         let pid = unsafe { libc::waitpid(pid, &mut status, opt) };
-        let pid = Errno::result(pid).map_err(|err| err.into_pyexception(vm))?;
+        let pid = nix::Error::result(pid).map_err(|err| err.into_pyexception(vm))?;
         Ok((pid, status))
     }
     #[pyfunction]
@@ -3158,6 +3157,7 @@ mod posix {
         who: PriorityWhoType,
         vm: &VirtualMachine,
     ) -> PyResult {
+        use nix::errno::{errno, Errno};
         Errno::clear();
         let retval = unsafe { libc::getpriority(which, who) };
         if errno() != 0 {
diff --git a/vm/src/stdlib/posixsubprocess.rs b/vm/src/stdlib/posixsubprocess.rs
index eff77bedb..f66793260 100644
--- a/vm/src/stdlib/posixsubprocess.rs
+++ b/vm/src/stdlib/posixsubprocess.rs
@@ -30,7 +30,7 @@ mod _posixsubprocess {
     }
 }
 
-use nix::{errno::Errno, fcntl, unistd};
+use nix::{errno::Errno, unistd};
 use std::convert::Infallible as Never;
 use std::ffi::{CStr, CString};
 use std::io::{self, prelude::*};
@@ -165,12 +165,13 @@ fn exec_inner(args: &ForkExecArgs, procargs: ProcArgs) -> nix::Result<Never> {
 
 #[cfg(not(target_os = "redox"))]
 fn close_fds(above: i32, keep: &[i32]) -> nix::Result<()> {
+    use nix::{dir::Dir, fcntl::OFlag};
     // TODO: close fds by brute force if readdir doesn't work:
     // https://github.com/python/cpython/blob/3.8/Modules/_posixsubprocess.c#L220
     let path = unsafe { CStr::from_bytes_with_nul_unchecked(FD_DIR_NAME) };
-    let mut dir = nix::dir::Dir::open(
+    let mut dir = Dir::open(
         path,
-        fcntl::OFlag::O_RDONLY | fcntl::OFlag::O_DIRECTORY,
+        OFlag::O_RDONLY | OFlag::O_DIRECTORY,
         nix::sys::stat::Mode::empty(),
     )?;
     let dirfd = dir.as_raw_fd();
@@ -196,6 +197,7 @@ const FD_DIR_NAME: &[u8] = b"/dev/fd\0";
 #[cfg(any(target_os = "linux", target_os = "android"))]
 const FD_DIR_NAME: &[u8] = b"/proc/self/fd\0";
 
+#[cfg(not(target_os = "redox"))]
 fn pos_int_from_ascii(name: &CStr) -> Option<i32> {
     let mut num = 0;
     for c in name.to_bytes() {