diff --git a/src/libstd/sys/unix/backtrace.rs b/src/libstd/sys/unix/backtrace.rs
index b46d390826c93..99a554a835f9f 100644
--- a/src/libstd/sys/unix/backtrace.rs
+++ b/src/libstd/sys/unix/backtrace.rs
@@ -122,9 +122,9 @@ pub fn write(w: &mut Write) -> io::Result<()> {
 
     try!(writeln!(w, "stack backtrace:"));
     // 100 lines should be enough
-    const SIZE: uint = 100;
+    const SIZE: usize = 100;
     let mut buf: [*mut libc::c_void; SIZE] = unsafe {mem::zeroed()};
-    let cnt = unsafe { backtrace(buf.as_mut_ptr(), SIZE as libc::c_int) as uint};
+    let cnt = unsafe { backtrace(buf.as_mut_ptr(), SIZE as libc::c_int) as usize};
 
     // skipping the first one as it is write itself
     let iter = (1..cnt).map(|i| {
diff --git a/src/libstd/sys/unix/os.rs b/src/libstd/sys/unix/os.rs
index 724156d81d84e..fab443feebd0b 100644
--- a/src/libstd/sys/unix/os.rs
+++ b/src/libstd/sys/unix/os.rs
@@ -339,7 +339,7 @@ pub fn args() -> Args {
         let info = objc_msgSend(klass, process_info_sel);
         let args = objc_msgSend(info, arguments_sel);
 
-        let cnt: int = mem::transmute(objc_msgSend(args, count_sel));
+        let cnt: usize = mem::transmute(objc_msgSend(args, count_sel));
         for i in (0..cnt) {
             let tmp = objc_msgSend(args, object_at_sel, i);
             let utf_c_str: *const libc::c_char =