diff --git a/src/libstd/old_io/mod.rs b/src/libstd/old_io/mod.rs
index 94f4af8e558..3673f590c0a 100644
--- a/src/libstd/old_io/mod.rs
+++ b/src/libstd/old_io/mod.rs
@@ -338,7 +338,7 @@ impl IoError {
     /// If `detail` is `true`, the `detail` field of the `IoError`
     /// struct is filled with an allocated string describing the error
     /// in more detail, retrieved from the operating system.
-    pub fn from_errno(errno: uint, detail: bool) -> IoError {
+    pub fn from_errno(errno: i32, detail: bool) -> IoError {
         let mut err = sys::decode_error(errno as i32);
         if detail && err.kind == OtherIoError {
             err.detail = Some(os::error_string(errno).chars()
@@ -354,7 +354,7 @@ impl IoError {
     /// operating system) between the call(s) for which errors are
     /// being checked and the call of this function.
     pub fn last_error() -> IoError {
-        IoError::from_errno(os::errno() as uint, true)
+        IoError::from_errno(os::errno(), true)
     }
 }
 
diff --git a/src/libstd/os.rs b/src/libstd/os.rs
index 2a0206d9ff0..3851e799713 100644
--- a/src/libstd/os.rs
+++ b/src/libstd/os.rs
@@ -514,8 +514,8 @@ pub fn change_dir(p: &Path) -> IoResult<()> {
 }
 
 /// Returns the platform-specific value of errno
-pub fn errno() -> uint {
-    sys::os::errno() as uint
+pub fn errno() -> i32 {
+    sys::os::errno() as i32
 }
 
 /// Return the string corresponding to an `errno()` value of `errnum`.
@@ -525,15 +525,15 @@ pub fn errno() -> uint {
 /// use std::os;
 ///
 /// // Same as println!("{}", last_os_error());
-/// println!("{}", os::error_string(os::errno() as uint));
+/// println!("{}", os::error_string(os::errno() as i32));
 /// ```
-pub fn error_string(errnum: uint) -> String {
-    return sys::os::error_string(errnum as i32);
+pub fn error_string(errnum: i32) -> String {
+    return sys::os::error_string(errnum);
 }
 
 /// Get a string representing the platform-dependent last error
 pub fn last_os_error() -> String {
-    error_string(errno() as uint)
+    error_string(errno())
 }
 
 /// Sets the process exit code
@@ -845,13 +845,13 @@ pub enum MapError {
     ErrAlreadyExists,
     /// Unrecognized error from `VirtualAlloc`. The inner value is the return
     /// value of GetLastError.
-    ErrVirtualAlloc(uint),
+    ErrVirtualAlloc(i32),
     /// Unrecognized error from `CreateFileMapping`. The inner value is the
     /// return value of `GetLastError`.
-    ErrCreateFileMappingW(uint),
+    ErrCreateFileMappingW(i32),
     /// Unrecognized error from `MapViewOfFile`. The inner value is the return
     /// value of `GetLastError`.
-    ErrMapViewOfFile(uint)
+    ErrMapViewOfFile(i32)
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
diff --git a/src/libstd/sys/unix/process.rs b/src/libstd/sys/unix/process.rs
index ab06109076e..32e45009887 100644
--- a/src/libstd/sys/unix/process.rs
+++ b/src/libstd/sys/unix/process.rs
@@ -394,7 +394,7 @@ impl Process {
                 match unsafe { c::select(max, &mut set, ptr::null_mut(),
                                          ptr::null_mut(), p) } {
                     // interrupted, retry
-                    -1 if os::errno() == libc::EINTR as uint => continue,
+                    -1 if os::errno() == libc::EINTR as i32 => continue,
 
                     // We read something, break out and process
                     1 | 2 => {}
diff --git a/src/libstd/sys/unix/timer.rs b/src/libstd/sys/unix/timer.rs
index 6a4e47f58ce..4cd98f4442b 100644
--- a/src/libstd/sys/unix/timer.rs
+++ b/src/libstd/sys/unix/timer.rs
@@ -198,7 +198,7 @@ fn helper(input: libc::c_int, messages: Receiver<Req>, _: ()) {
                 assert_eq!(fd.read(&mut buf).ok().unwrap(), 1);
             }
 
-            -1 if os::errno() == libc::EINTR as uint => {}
+            -1 if os::errno() == libc::EINTR as i32 => {}
             n => panic!("helper thread failed in select() with error: {} ({})",
                        n, os::last_os_error())
         }