diff --git a/src/libstd/rt/mod.rs b/src/libstd/rt/mod.rs
index fec555e8afd..8713cf05a47 100644
--- a/src/libstd/rt/mod.rs
+++ b/src/libstd/rt/mod.rs
@@ -58,6 +58,7 @@ Several modules in `core` are clients of `rt`:
 #[deny(unused_imports)];
 #[deny(unused_mut)];
 #[deny(unused_variable)];
+#[deny(unused_unsafe)];
 
 use cell::Cell;
 use clone::Clone;
@@ -224,7 +225,7 @@ pub fn run(main: ~fn()) -> int {
 
     let nthreads = match os::getenv("RUST_THREADS") {
         Some(nstr) => FromStr::from_str(nstr).get(),
-        None => unsafe { util::num_cpus() }
+        None => util::num_cpus()
     };
 
     // The shared list of sleeping schedulers. Schedulers wake each other
diff --git a/src/libstd/rt/test.rs b/src/libstd/rt/test.rs
index 36efcd91834..b0e49684014 100644
--- a/src/libstd/rt/test.rs
+++ b/src/libstd/rt/test.rs
@@ -74,7 +74,7 @@ pub fn run_in_mt_newsched_task(f: ~fn()) {
     do run_in_bare_thread {
         let nthreads = match os::getenv("RUST_TEST_THREADS") {
             Some(nstr) => FromStr::from_str(nstr).get(),
-            None => unsafe {
+            None => {
                 // Using more threads than cores in test code
                 // to force the OS to preempt them frequently.
                 // Assuming that this help stress test concurrent types.
diff --git a/src/libstd/rt/uv/timer.rs b/src/libstd/rt/uv/timer.rs
index cd6fc5c0a25..14465eb7dfd 100644
--- a/src/libstd/rt/uv/timer.rs
+++ b/src/libstd/rt/uv/timer.rs
@@ -160,14 +160,14 @@ mod test {
                         let mut timer2 = TimerWatcher::new(&mut loop_);
                         do timer2.start(10, 0) |timer2, _| {
 
-                            unsafe { *count_ptr += 1; }
+                            *count_ptr += 1;
 
                             timer2.close(||());
 
                             // Restart the original timer
                             let mut timer = timer;
                             do timer.start(1, 0) |timer, _| {
-                                unsafe { *count_ptr += 1; }
+                                *count_ptr += 1;
                                 timer.close(||());
                             }
                         }