diff --git a/src/comp/middle/trans_build.rs b/src/comp/middle/trans_build.rs
index 196d6a34fcbc..c0e7e19c1d7f 100644
--- a/src/comp/middle/trans_build.rs
+++ b/src/comp/middle/trans_build.rs
@@ -81,7 +81,7 @@ fn IndirectBr(cx: @block_ctxt, Addr: ValueRef, NumDests: uint) {
 
 // This is a really awful way to get a zero-length c-string, but better (and a
 // lot more efficient) than doing str::as_buf("", ...) every time.
-fn noname() -> sbuf {
+fn noname() -> sbuf unsafe {
     const cnull: uint = 0u;
     ret std::unsafe::reinterpret_cast(std::ptr::addr_of(cnull));
 }
@@ -480,9 +480,11 @@ fn Phi(cx: @block_ctxt, Ty: TypeRef, vals: [ValueRef], bbs: [BasicBlockRef])
 
 fn AddIncomingToPhi(phi: ValueRef, val: ValueRef, bb: BasicBlockRef) {
     if llvm::LLVMIsUndef(phi) == lib::llvm::True { ret; }
-    let valptr = std::unsafe::reinterpret_cast(std::ptr::addr_of(val));
-    let bbptr = std::unsafe::reinterpret_cast(std::ptr::addr_of(bb));
-    llvm::LLVMAddIncoming(phi, valptr, bbptr, 1u);
+    unsafe {
+        let valptr = std::unsafe::reinterpret_cast(std::ptr::addr_of(val));
+        let bbptr = std::unsafe::reinterpret_cast(std::ptr::addr_of(bb));
+        llvm::LLVMAddIncoming(phi, valptr, bbptr, 1u);
+    }
 }
 
 fn _UndefReturn(Fn: ValueRef) -> ValueRef {
diff --git a/src/lib/box.rs b/src/lib/box.rs
index 821a8428d2c9..6682fe17284a 100644
--- a/src/lib/box.rs
+++ b/src/lib/box.rs
@@ -11,7 +11,10 @@ Function: ptr_eq
 Determine if two shared boxes point to the same object
 */
 fn ptr_eq<T>(a: @T, b: @T) -> bool {
-    let a_ptr: uint = unsafe::reinterpret_cast(a);
-    let b_ptr: uint = unsafe::reinterpret_cast(b);
-    ret a_ptr == b_ptr;
+    // FIXME: ptr::addr_of
+    unsafe {
+        let a_ptr: uint = unsafe::reinterpret_cast(a);
+        let b_ptr: uint = unsafe::reinterpret_cast(b);
+        ret a_ptr == b_ptr;
+    }
 }
diff --git a/src/lib/ptr.rs b/src/lib/ptr.rs
index 35644ab840b1..5c3768311380 100644
--- a/src/lib/ptr.rs
+++ b/src/lib/ptr.rs
@@ -29,4 +29,4 @@ Function: null
 
 Create an unsafe null pointer
 */
-fn null<T>() -> *T { ret unsafe::reinterpret_cast(0u); }
+fn null<T>() -> *T unsafe { ret unsafe::reinterpret_cast(0u); }
diff --git a/src/lib/run_program.rs b/src/lib/run_program.rs
index e4913b54184f..c308f4957d04 100644
--- a/src/lib/run_program.rs
+++ b/src/lib/run_program.rs
@@ -92,7 +92,8 @@ type program = obj {
 fn arg_vec(prog: str, args: [@str]) -> [sbuf] {
     let argptrs = str::as_buf(prog, {|buf| [buf] });
     for arg in args { argptrs += str::as_buf(*arg, {|buf| [buf] }); }
-    argptrs += [unsafe::reinterpret_cast(0)];
+    // FIXME: ptr::null instead of cast
+    argptrs += [unsafe {unsafe::reinterpret_cast(0)}];
     ret argptrs;
 }
 
diff --git a/src/lib/str.rs b/src/lib/str.rs
index 1b759ffb8cfd..29ee1b9340fa 100644
--- a/src/lib/str.rs
+++ b/src/lib/str.rs
@@ -127,7 +127,7 @@ Function: byte_len
 
 Returns the length in bytes of a string
 */
-fn byte_len(s: str) -> uint {
+fn byte_len(s: str) -> uint unsafe {
     let v: [u8] = unsafe::reinterpret_cast(s);
     let vlen = vec::len(v);
     unsafe::leak(v);
@@ -141,7 +141,7 @@ Function: bytes
 
 Converts a string to a vector of bytes
 */
-fn bytes(s: str) -> [u8] {
+fn bytes(s: str) -> [u8] unsafe {
     let v = unsafe::reinterpret_cast(s);
     let vcopy = vec::slice(v, 0u, vec::len(v) - 1u);
     unsafe::leak(v);
@@ -154,7 +154,7 @@ Function: unsafe_from_bytes
 Converts a vector of bytes to a string. Does not verify that the
 vector contains valid UTF-8.
 */
-fn unsafe_from_bytes(v: [mutable? u8]) -> str {
+fn unsafe_from_bytes(v: [mutable? u8]) -> str unsafe {
     let vcopy: [u8] = v + [0u8];
     let scopy: str = unsafe::reinterpret_cast(vcopy);
     unsafe::leak(vcopy);
@@ -520,7 +520,7 @@ Failure:
 - If begin is greater than end.
 - If end is greater than the length of the string.
 */
-fn slice(s: str, begin: uint, end: uint) -> str {
+fn slice(s: str, begin: uint, end: uint) -> str unsafe {
     // FIXME: Typestate precondition
     assert (begin <= end);
     assert (end <= byte_len(s));
diff --git a/src/lib/task.rs b/src/lib/task.rs
index 1b5ebb999cfa..304cf59f81d7 100644
--- a/src/lib/task.rs
+++ b/src/lib/task.rs
@@ -273,9 +273,9 @@ fn spawn_joinable<uniq T>(-data: T, f: fn(T)) -> joinable_task {
 
 fn spawn_inner<uniq T>(-data: T, f: fn(T),
                           notify: option<comm::chan<task_notification>>)
-    -> task {
+    -> task unsafe {
 
-    fn wrapper<uniq T>(-data: *u8, f: fn(T)) {
+    fn wrapper<uniq T>(-data: *u8, f: fn(T)) unsafe {
         let data: ~T = unsafe::reinterpret_cast(data);
         f(*data);
     }
diff --git a/src/lib/unsafe.rs b/src/lib/unsafe.rs
index 0259555adc4a..1a6f87575763 100644
--- a/src/lib/unsafe.rs
+++ b/src/lib/unsafe.rs
@@ -17,7 +17,7 @@ Function: reinterpret_cast
 
 Casts the value at `src` to U. The two types must have the same length.
 */
-fn reinterpret_cast<T, U>(src: T) -> U { ret rusti::cast(src); }
+unsafe fn reinterpret_cast<T, U>(src: T) -> U { ret rusti::cast(src); }
 
 /*
 Function: leak
@@ -29,4 +29,4 @@ to run any required cleanup or memory-management operations on it. This
 can be used for various acts of magick, particularly when using
 reinterpret_cast on managed pointer types.
 */
-fn leak<T>(-thing: T) { rustrt::leak(thing); }
+unsafe fn leak<T>(-thing: T) { rustrt::leak(thing); }