diff --git a/src/lib.rs b/src/lib.rs
index 1fc01ea..1b101ab 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -55,7 +55,7 @@ use std::thread::{self, JoinHandle};
 use std::sync::mpsc::{channel, Sender, Receiver, SyncSender, sync_channel, RecvError};
 use std::sync::{Arc, Mutex};
 use std::marker::PhantomData;
-use std::mem;
+use std::mem::{self, ManuallyDrop};
 
 enum Message {
     NewJob(Thunk<'static>),
@@ -76,7 +76,11 @@ type Thunk<'a> = Box<FnBox + Send + 'a>;
 
 impl Drop for Pool {
     fn drop(&mut self) {
-        self.job_sender = None;
+        // Explicitly drop job_sender before the threads, to ensure
+        // channel is already closed by the time threads are joined.
+        unsafe {
+            ManuallyDrop::drop(&mut self.job_sender);
+        }
     }
 }
 
@@ -84,7 +88,7 @@ impl Drop for Pool {
 /// of threads spawned at construction.
 pub struct Pool {
     threads: Vec<ThreadData>,
-    job_sender: Option<Sender<Message>>
+    job_sender: ManuallyDrop<Sender<Message>>,
 }
 
 struct ThreadData {
@@ -162,7 +166,7 @@ impl Pool {
 
         Pool {
             threads: threads,
-            job_sender: Some(job_sender),
+            job_sender: ManuallyDrop::new(job_sender),
         }
     }
 
@@ -210,13 +214,13 @@ impl<'pool, 'scope> Scope<'pool, 'scope> {
         let b = unsafe {
             mem::transmute::<Thunk<'scope>, Thunk<'static>>(Box::new(f))
         };
-        self.pool.job_sender.as_ref().unwrap().send(Message::NewJob(b)).unwrap();
+        self.pool.job_sender.send(Message::NewJob(b)).unwrap();
     }
 
     /// Blocks until all currently queued jobs have run to completion.
     pub fn join_all(&self) {
         for _ in 0..self.pool.threads.len() {
-            self.pool.job_sender.as_ref().unwrap().send(Message::Join).unwrap();
+            self.pool.job_sender.send(Message::Join).unwrap();
         }
 
         // Synchronize/Join with threads