diff --git a/src/liballoc_jemalloc/lib.rs b/src/liballoc_jemalloc/lib.rs
index 2a68fa1046a1f..045044916b929 100644
--- a/src/liballoc_jemalloc/lib.rs
+++ b/src/liballoc_jemalloc/lib.rs
@@ -81,7 +81,7 @@ pub extern fn __rust_reallocate(ptr: *mut u8, _old_size: usize, size: usize,
 pub extern fn __rust_reallocate_inplace(ptr: *mut u8, _old_size: usize,
                                         size: usize, align: usize) -> usize {
     let flags = align_to_flags(align);
-    unsafe { je_xallocx(ptr as *mut c_void, size, 0, flags) as usize }
+    unsafe { je_xallocx(ptr as *mut c_void, size, 0, flags) }
 }
 
 #[no_mangle]
@@ -93,5 +93,5 @@ pub extern fn __rust_deallocate(ptr: *mut u8, old_size: usize, align: usize) {
 #[no_mangle]
 pub extern fn __rust_usable_size(size: usize, align: usize) -> usize {
     let flags = align_to_flags(align);
-    unsafe { je_nallocx(size, flags) as usize }
+    unsafe { je_nallocx(size, flags) }
 }
diff --git a/src/liblibc/lib.rs b/src/liblibc/lib.rs
index 3f2e9fb116ff8..e872aa9c92cd7 100644
--- a/src/liblibc/lib.rs
+++ b/src/liblibc/lib.rs
@@ -4749,7 +4749,7 @@ pub mod consts {
 
             pub const PTHREAD_CREATE_JOINABLE : c_int = 0;
             pub const PTHREAD_CREATE_DETACHED : c_int = 1;
-            pub const PTHREAD_STACK_MIN : size_t = 2048;
+            pub const PTHREAD_STACK_MIN: size_t = 2048;
 
             pub const CLOCK_REALTIME : c_int = 0;
             pub const CLOCK_MONOTONIC : c_int = 3;
diff --git a/src/libstd/sys/unix/os.rs b/src/libstd/sys/unix/os.rs
index d87f53e69711d..de23d1e69cf92 100644
--- a/src/libstd/sys/unix/os.rs
+++ b/src/libstd/sys/unix/os.rs
@@ -196,13 +196,13 @@ pub fn current_exe() -> io::Result<PathBuf> {
                          ptr::null_mut(), &mut sz, ptr::null_mut(), 0);
         if err != 0 { return Err(io::Error::last_os_error()); }
         if sz == 0 { return Err(io::Error::last_os_error()); }
-        let mut v: Vec<u8> = Vec::with_capacity(sz as usize);
+        let mut v: Vec<u8> = Vec::with_capacity(sz);
         let err = sysctl(mib.as_mut_ptr(), mib.len() as ::libc::c_uint,
                          v.as_mut_ptr() as *mut libc::c_void, &mut sz,
                          ptr::null_mut(), 0);
         if err != 0 { return Err(io::Error::last_os_error()); }
         if sz == 0 { return Err(io::Error::last_os_error()); }
-        v.set_len(sz as usize - 1); // chop off trailing NUL
+        v.set_len(sz - 1); // chop off trailing NUL
         Ok(PathBuf::from(OsString::from_vec(v)))
     }
 }
@@ -246,10 +246,10 @@ pub fn current_exe() -> io::Result<PathBuf> {
         let mut sz: u32 = 0;
         _NSGetExecutablePath(ptr::null_mut(), &mut sz);
         if sz == 0 { return Err(io::Error::last_os_error()); }
-        let mut v: Vec<u8> = Vec::with_capacity(sz as usize);
+        let mut v: Vec<u8> = Vec::with_capacity(sz);
         let err = _NSGetExecutablePath(v.as_mut_ptr() as *mut i8, &mut sz);
         if err != 0 { return Err(io::Error::last_os_error()); }
-        v.set_len(sz as usize - 1); // chop off trailing NUL
+        v.set_len(sz - 1); // chop off trailing NUL
         Ok(PathBuf::from(OsString::from_vec(v)))
     }
 }
diff --git a/src/libstd/sys/unix/thread.rs b/src/libstd/sys/unix/thread.rs
index 283d228063390..448799bad2b75 100644
--- a/src/libstd/sys/unix/thread.rs
+++ b/src/libstd/sys/unix/thread.rs
@@ -360,8 +360,8 @@ fn min_stack_size(attr: *const libc::pthread_attr_t) -> usize {
     });
 
     match unsafe { __pthread_get_minstack } {
-        None => PTHREAD_STACK_MIN as usize,
-        Some(f) => unsafe { f(attr) as usize },
+        None => PTHREAD_STACK_MIN,
+        Some(f) => unsafe { f(attr) },
     }
 }
 
@@ -369,7 +369,7 @@ fn min_stack_size(attr: *const libc::pthread_attr_t) -> usize {
 // platforms.
 #[cfg(not(target_os = "linux"))]
 fn min_stack_size(_: *const libc::pthread_attr_t) -> usize {
-    PTHREAD_STACK_MIN as usize
+    PTHREAD_STACK_MIN
 }
 
 extern {
diff --git a/src/test/compile-fail/warn-foreign-int-types.rs b/src/test/compile-fail/warn-foreign-int-types.rs
index b77f25a0a344f..eff154dcfc6cf 100644
--- a/src/test/compile-fail/warn-foreign-int-types.rs
+++ b/src/test/compile-fail/warn-foreign-int-types.rs
@@ -13,9 +13,11 @@
 
 mod xx {
     extern {
-        pub fn strlen(str: *const u8) -> usize; //~ ERROR found Rust type `usize`
-        pub fn foo(x: isize, y: usize); //~ ERROR found Rust type `isize`
-        //~^ ERROR found Rust type `usize`
+        pub fn strlen_good(str: *const u8) -> usize; // `usize` is OK.
+        pub fn strlen_bad(str: *const char) -> usize; //~ ERROR found Rust type `char`
+        pub fn foo(x: isize, y: usize); // `isize` is OK.
+        pub fn bar(x: &[u8]); //~ ERROR found Rust slice type
+        //~^ ERROR found Rust type `char`
     }
 }