diff --git a/src/libgreen/simple.rs b/src/libgreen/simple.rs
index ddacc11fd9edd..4a0523fe47a7a 100644
--- a/src/libgreen/simple.rs
+++ b/src/libgreen/simple.rs
@@ -75,7 +75,7 @@ impl Runtime for SimpleTask {
         fail!()
     }
     fn local_io<'a>(&'a mut self) -> Option<rtio::LocalIo<'a>> { None }
-    fn stack_bounds(&self) -> Option<(uint, uint)> { None }
+    fn stack_bounds(&self) -> (uint, uint) { fail!() }
     fn wrap(~self) -> ~Any { fail!() }
 }
 
diff --git a/src/libgreen/task.rs b/src/libgreen/task.rs
index 183fe8d055528..e1db24e11e472 100644
--- a/src/libgreen/task.rs
+++ b/src/libgreen/task.rs
@@ -450,11 +450,12 @@ impl Runtime for GreenTask {
         }
     }
 
-    fn stack_bounds(&self) -> Option<(uint, uint)> {
-        self.coroutine.as_ref().map(|c| {
-            (c.current_stack_segment.start() as uint,
-             c.current_stack_segment.end() as uint)
-        })
+    fn stack_bounds(&self) -> (uint, uint) {
+        let c = self.coroutine.as_ref()
+            .expect("GreenTask.stack_bounds called without a coroutine");
+
+        (c.current_stack_segment.start() as uint,
+         c.current_stack_segment.end() as uint)
     }
 
     fn wrap(~self) -> ~Any { self as ~Any }
diff --git a/src/libnative/lib.rs b/src/libnative/lib.rs
index 9c30e94194dd2..d4447fb7f2137 100644
--- a/src/libnative/lib.rs
+++ b/src/libnative/lib.rs
@@ -33,6 +33,13 @@ mod bookeeping;
 pub mod io;
 pub mod task;
 
+#[cfg(windows)]
+#[cfg(android)]
+static OS_DEFAULT_STACK_ESTIMATE: uint = 1 << 20;
+#[cfg(unix, not(android))]
+static OS_DEFAULT_STACK_ESTIMATE: uint = 2 * (1 << 20);
+
+
 // XXX: this should not exist here
 #[cfg(stage0)]
 #[lang = "start"]
@@ -66,10 +73,19 @@ pub fn lang_start(main: *u8, argc: int, argv: **u8) -> int {
 /// This function will only return once *all* native threads in the system have
 /// exited.
 pub fn start(argc: int, argv: **u8, main: proc()) -> int {
+    let something_around_the_top_of_the_stack = 1;
+    let addr = &something_around_the_top_of_the_stack as *int;
+    let my_stack_top = addr as uint;
+
+    // FIXME #11359 we just assume that this thread has a stack of a
+    // certain size, and estimate that there's at most 20KB of stack
+    // frames above our current position.
+    let my_stack_bottom = my_stack_top + 20000 - OS_DEFAULT_STACK_ESTIMATE;
+
     rt::init(argc, argv);
     let mut exit_code = None;
     let mut main = Some(main);
-    task::new().run(|| {
+    task::new((my_stack_bottom, my_stack_top)).run(|| {
         exit_code = Some(run(main.take_unwrap()));
     });
     unsafe { rt::cleanup(); }
diff --git a/src/libnative/task.rs b/src/libnative/task.rs
index 5a1ef5c836e16..73ad5618e3a9d 100644
--- a/src/libnative/task.rs
+++ b/src/libnative/task.rs
@@ -30,9 +30,11 @@ use task;
 use bookeeping;
 
 /// Creates a new Task which is ready to execute as a 1:1 task.
-pub fn new() -> ~Task {
+pub fn new(stack_bounds: (uint, uint)) -> ~Task {
     let mut task = ~Task::new();
-    task.put_runtime(ops() as ~rt::Runtime);
+    let mut ops = ops();
+    ops.stack_bounds = stack_bounds;
+    task.put_runtime(ops as ~rt::Runtime);
     return task;
 }
 
@@ -41,7 +43,8 @@ fn ops() -> ~Ops {
         lock: unsafe { Mutex::new() },
         awoken: false,
         io: io::IoFactory::new(),
-        stack_bounds: None,
+        // these *should* get overwritten
+        stack_bounds: (0, 0),
     }
 }
 
@@ -91,7 +94,7 @@ pub fn spawn_opts(opts: TaskOpts, f: proc()) {
             stack::record_stack_bounds(my_stack - stack + 1024, my_stack);
         }
         let mut ops = ops;
-        ops.stack_bounds = Some((my_stack - stack + 1024, my_stack));
+        ops.stack_bounds = (my_stack - stack + 1024, my_stack);
 
         let mut f = Some(f);
         let mut task = task;
@@ -111,7 +114,7 @@ struct Ops {
     // This field holds the known bounds of the stack in (lo, hi) form. Not all
     // native tasks necessarily know their precise bounds, hence this is
     // optional.
-    stack_bounds: Option<(uint, uint)>,
+    stack_bounds: (uint, uint),
 }
 
 impl rt::Runtime for Ops {
@@ -133,7 +136,7 @@ impl rt::Runtime for Ops {
         self as ~Any
     }
 
-    fn stack_bounds(&self) -> Option<(uint, uint)> { self.stack_bounds }
+    fn stack_bounds(&self) -> (uint, uint) { self.stack_bounds }
 
     // This function gets a little interesting. There are a few safety and
     // ownership violations going on here, but this is all done in the name of
diff --git a/src/libstd/rt/mod.rs b/src/libstd/rt/mod.rs
index 050caef86ebdb..95e39872b7476 100644
--- a/src/libstd/rt/mod.rs
+++ b/src/libstd/rt/mod.rs
@@ -159,7 +159,8 @@ pub trait Runtime {
     // you're in.
     fn spawn_sibling(~self, cur_task: ~Task, opts: TaskOpts, f: proc());
     fn local_io<'a>(&'a mut self) -> Option<rtio::LocalIo<'a>>;
-    fn stack_bounds(&self) -> Option<(uint, uint)>; // (lo, hi)
+    /// The (low, high) edges of the current stack.
+    fn stack_bounds(&self) -> (uint, uint); // (lo, hi)
 
     // XXX: This is a serious code smell and this should not exist at all.
     fn wrap(~self) -> ~Any;
diff --git a/src/libstd/rt/task.rs b/src/libstd/rt/task.rs
index 3efa979e51515..6fb1d11101556 100644
--- a/src/libstd/rt/task.rs
+++ b/src/libstd/rt/task.rs
@@ -285,7 +285,7 @@ impl Task {
     /// Returns the stack bounds for this task in (lo, hi) format. The stack
     /// bounds may not be known for all tasks, so the return value may be
     /// `None`.
-    pub fn stack_bounds(&self) -> Option<(uint, uint)> {
+    pub fn stack_bounds(&self) -> (uint, uint) {
         self.imp.get_ref().stack_bounds()
     }
 }