diff --git a/doc/tutorial/ffi.md b/doc/tutorial/ffi.md
index 9b42a3dd601..4c4ad0eba7b 100644
--- a/doc/tutorial/ffi.md
+++ b/doc/tutorial/ffi.md
@@ -162,9 +162,10 @@ This program uses the Posix function `gettimeofday` to get a
 microsecond-resolution timer.
 
     use std;
-    type timeval = {tv_sec: u32, tv_usec: u32};
+    type timeval = {mutable tv_sec: u32,
+                    mutable tv_usec: u32};
     native "cdecl" mod libc = "" {
-        fn gettimeofday(tv: *mutable timeval, tz: *()) -> i32;
+        fn gettimeofday(tv: *timeval, tz: *()) -> i32;
     }
     fn unix_time_in_microseconds() -> u64 unsafe {
         let x = {tv_sec: 0u32, tv_usec: 0u32};
diff --git a/src/lib/linux_os.rs b/src/lib/linux_os.rs
index 49f029052d6..b2c93beb643 100644
--- a/src/lib/linux_os.rs
+++ b/src/lib/linux_os.rs
@@ -64,7 +64,7 @@ fn dylib_filename(base: str) -> str { ret "lib" + base + ".so"; }
 
 fn pipe() -> {in: int, out: int} {
     let fds = {mutable in: 0, mutable out: 0};
-    assert (os::libc::pipe(ptr::addr_of(fds.in)) == 0);
+    assert (os::libc::pipe(ptr::mut_addr_of(fds.in)) == 0);
     ret {in: fds.in, out: fds.out};
 }
 
diff --git a/src/lib/macos_os.rs b/src/lib/macos_os.rs
index f8f19b77387..9de76a170d5 100644
--- a/src/lib/macos_os.rs
+++ b/src/lib/macos_os.rs
@@ -57,7 +57,7 @@ fn dylib_filename(base: str) -> str { ret "lib" + base + ".dylib"; }
 
 fn pipe() -> {in: int, out: int} {
     let fds = {mutable in: 0, mutable out: 0};
-    assert (os::libc::pipe(ptr::addr_of(fds.in)) == 0);
+    assert (os::libc::pipe(ptr::mut_addr_of(fds.in)) == 0);
     ret {in: fds.in, out: fds.out};
 }
 
@@ -82,7 +82,8 @@ fn get_exe_path() -> option::t<fs::path> {
     let bufsize = 1023u32;
     let path = str::unsafe_from_bytes(vec::init_elt(0u8, bufsize as uint));
     ret str::as_buf(path, { |path_buf|
-        if libc::_NSGetExecutablePath(path_buf, ptr::addr_of(bufsize)) == 0 {
+        if libc::_NSGetExecutablePath(path_buf,
+                                      ptr::mut_addr_of(bufsize)) == 0 {
             option::some(fs::dirname(path) + fs::path_sep())
         } else {
             option::none
diff --git a/src/lib/ptr.rs b/src/lib/ptr.rs
index 5c376831138..df30105b11d 100644
--- a/src/lib/ptr.rs
+++ b/src/lib/ptr.rs
@@ -4,7 +4,7 @@ Module: ptr
 Unsafe pointer utility functions
 */
 native "rust-intrinsic" mod rusti {
-    fn addr_of<T>(val: T) -> *mutable T;
+    fn addr_of<T>(val: T) -> *T;
     fn ptr_offset<T>(ptr: *T, count: uint) -> *T;
 }
 
@@ -13,7 +13,16 @@ Function: addr_of
 
 Get an unsafe pointer to a value
 */
-fn addr_of<T>(val: T) -> *mutable T { ret rusti::addr_of(val); }
+fn addr_of<T>(val: T) -> *T { ret rusti::addr_of(val); }
+
+/*
+Function: mut_addr_of
+
+Get an unsafe mutable pointer to a value
+*/
+fn mut_addr_of<T>(val: T) -> *mutable T unsafe {
+    ret unsafe::reinterpret_cast(rusti::addr_of(val));
+}
 
 /*
 Function: offset
diff --git a/src/lib/win32_os.rs b/src/lib/win32_os.rs
index eaa895f1ef1..9cbb8adb5b6 100644
--- a/src/lib/win32_os.rs
+++ b/src/lib/win32_os.rs
@@ -66,7 +66,7 @@ fn pipe() -> {in: int, out: int} {
     // first, as in rust_run_program.
     let fds = {mutable in: 0, mutable out: 0};
     let res =
-        os::libc::_pipe(ptr::addr_of(fds.in), 1024u,
+        os::libc::_pipe(ptr::mut_addr_of(fds.in), 1024u,
                         libc_constants::O_BINARY() |
                             libc_constants::O_NOINHERIT());
     assert (res == 0);
diff --git a/src/test/compile-fail/mutable-huh-ptr-assign.rs b/src/test/compile-fail/mutable-huh-ptr-assign.rs
index 964a57a19db..fdd2cbb9705 100644
--- a/src/test/compile-fail/mutable-huh-ptr-assign.rs
+++ b/src/test/compile-fail/mutable-huh-ptr-assign.rs
@@ -10,7 +10,7 @@ fn main() {
 
     unsafe {
         let a = 0;
-        let v = std::ptr::addr_of(a);
+        let v = std::ptr::mut_addr_of(a);
         f(v);
     }
 }
diff --git a/src/test/compile-fail/mutable-huh-variance-ptr.rs b/src/test/compile-fail/mutable-huh-variance-ptr.rs
index b515f5aad7d..8f19ebd1dff 100644
--- a/src/test/compile-fail/mutable-huh-variance-ptr.rs
+++ b/src/test/compile-fail/mutable-huh-variance-ptr.rs
@@ -4,7 +4,7 @@ use std;
 
 fn main() {
     let a = [0];
-    let v: *mutable [int] = std::ptr::addr_of(a);
+    let v: *mutable [int] = std::ptr::mut_addr_of(a);
 
     fn f(&&v: *mutable [mutable? int]) {
         unsafe {
diff --git a/src/test/stdtest/ptr.rs b/src/test/stdtest/ptr.rs
index ac829f90e5f..6a353bcdeea 100644
--- a/src/test/stdtest/ptr.rs
+++ b/src/test/stdtest/ptr.rs
@@ -7,7 +7,7 @@ type pair = {mutable fst: int, mutable snd: int};
 #[test]
 fn test() unsafe {
     let p = {mutable fst: 10, mutable snd: 20};
-    let pptr: *mutable pair = ptr::addr_of(p);
+    let pptr: *mutable pair = ptr::mut_addr_of(p);
     let iptr: *mutable int = unsafe::reinterpret_cast(pptr);
     assert (*iptr == 10);;
     *iptr = 30;