diff --git a/timely/src/dataflow/channels/mod.rs b/timely/src/dataflow/channels/mod.rs
index 641f0a190..acb3dd9de 100644
--- a/timely/src/dataflow/channels/mod.rs
+++ b/timely/src/dataflow/channels/mod.rs
@@ -52,9 +52,4 @@ impl<T, D> Message<T, D> {
                 buffer.clear();
             }
         }
-
-        // TODO: Unclear we always want this here.
-        if buffer.capacity() != Self::default_length() {
-            *buffer = Vec::with_capacity(Self::default_length());
-        }
     }}
diff --git a/timely/src/dataflow/channels/pushers/buffer.rs b/timely/src/dataflow/channels/pushers/buffer.rs
index 288d5ff88..603d07164 100644
--- a/timely/src/dataflow/channels/pushers/buffer.rs
+++ b/timely/src/dataflow/channels/pushers/buffer.rs
@@ -23,7 +23,7 @@ impl<T, D, P: Push<Bundle<T, D>>> Buffer<T, D, P> where T: Eq+Clone {
     pub fn new(pusher: P) -> Buffer<T, D, P> {
         Buffer {
             time: None,
-            buffer: Vec::with_capacity(Message::<T, D>::default_length()),
+            buffer: Vec::new(),
             pusher,
         }
     }
@@ -53,6 +53,7 @@ impl<T, D, P: Push<Bundle<T, D>>> Buffer<T, D, P> where T: Eq+Clone {
     pub fn cease(&mut self) {
         self.flush();
         self.pusher.push(&mut None);
+        self.buffer = Vec::new();
     }
 
     /// moves the contents of
@@ -65,6 +66,9 @@ impl<T, D, P: Push<Bundle<T, D>>> Buffer<T, D, P> where T: Eq+Clone {
 
     // internal method for use by `Session`.
     fn give(&mut self, data: D) {
+        if self.buffer.capacity() == 0 {
+            self.buffer = Vec::with_capacity(Message::<T, D>::default_length());
+        }
         self.buffer.push(data);
         // assert!(self.buffer.capacity() == Message::<O::Data>::default_length());
         if self.buffer.len() == self.buffer.capacity() {
diff --git a/timely/src/dataflow/channels/pushers/exchange.rs b/timely/src/dataflow/channels/pushers/exchange.rs
index 5b37a8438..08dc45b3d 100644
--- a/timely/src/dataflow/channels/pushers/exchange.rs
+++ b/timely/src/dataflow/channels/pushers/exchange.rs
@@ -18,7 +18,7 @@ impl<T: Clone, D, P: Push<Bundle<T, D>>, H: FnMut(&T, &D)->u64>  Exchange<T, D,
     pub fn new(pushers: Vec<P>, key: H) -> Exchange<T, D, P, H> {
         let mut buffers = vec![];
         for _ in 0..pushers.len() {
-            buffers.push(Vec::with_capacity(Message::<T, D>::default_length()));
+            buffers.push(Vec::new());
         }
         Exchange {
             pushers,
@@ -64,6 +64,9 @@ impl<T: Eq+Data, D: Data, P: Push<Bundle<T, D>>, H: FnMut(&T, &D)->u64> Push<Bun
                 for datum in data.drain(..) {
                     let index = (((self.hash_func)(time, &datum)) & mask) as usize;
 
+                    if self.buffers[index].capacity() == 0 {
+                        self.buffers[index] = Vec::with_capacity(Message::<T, D>::default_length());
+                    }
                     self.buffers[index].push(datum);
                     if self.buffers[index].len() == self.buffers[index].capacity() {
                         self.flush(index);
@@ -82,6 +85,9 @@ impl<T: Eq+Data, D: Data, P: Push<Bundle<T, D>>, H: FnMut(&T, &D)->u64> Push<Bun
             else {
                 for datum in data.drain(..) {
                     let index = (((self.hash_func)(time, &datum)) % self.pushers.len() as u64) as usize;
+                    if self.buffers[index].capacity() == 0 {
+                        self.buffers[index] = Vec::with_capacity(Message::<T, D>::default_length());
+                    }
                     self.buffers[index].push(datum);
                     if self.buffers[index].len() == self.buffers[index].capacity() {
                         self.flush(index);
@@ -95,6 +101,8 @@ impl<T: Eq+Data, D: Data, P: Push<Bundle<T, D>>, H: FnMut(&T, &D)->u64> Push<Bun
             for index in 0..self.pushers.len() {
                 self.flush(index);
                 self.pushers[index].push(&mut None);
+                // Free up buffer space.
+                self.buffers[index] = Vec::new();
             }
         }
     }
diff --git a/timely/src/dataflow/channels/pushers/tee.rs b/timely/src/dataflow/channels/pushers/tee.rs
index f5e3915ea..f31496ff0 100644
--- a/timely/src/dataflow/channels/pushers/tee.rs
+++ b/timely/src/dataflow/channels/pushers/tee.rs
@@ -31,6 +31,8 @@ impl<T: Data, D: Data> Push<Bundle<T, D>> for Tee<T, D> {
             for index in 1..pushers.len() {
                 pushers[index-1].push(&mut None);
             }
+            // Free up buffer space.
+            self.buffer = Vec::new();
         }
         if pushers.len() > 0 {
             let last = pushers.len() - 1;
@@ -44,7 +46,7 @@ impl<T, D> Tee<T, D> {
     pub fn new() -> (Tee<T, D>, TeeHelper<T, D>) {
         let shared = Rc::new(RefCell::new(Vec::new()));
         let port = Tee {
-            buffer: Vec::with_capacity(Message::<T, D>::default_length()),
+            buffer: Vec::new(),
             shared: shared.clone(),
         };
 
diff --git a/timely/src/dataflow/operators/input.rs b/timely/src/dataflow/operators/input.rs
index 11d02896d..e59a52c28 100644
--- a/timely/src/dataflow/operators/input.rs
+++ b/timely/src/dataflow/operators/input.rs
@@ -212,8 +212,8 @@ impl<T:Timestamp, D: Data> Handle<T, D> {
             activate: Vec::new(),
             progress: Vec::new(),
             pushers: Vec::new(),
-            buffer1: Vec::with_capacity(Message::<T, D>::default_length()),
-            buffer2: Vec::with_capacity(Message::<T, D>::default_length()),
+            buffer1: Vec::new(),
+            buffer2: Vec::new(),
             now_at: T::minimum(),
         }
     }
@@ -288,7 +288,11 @@ impl<T:Timestamp, D: Data> Handle<T, D> {
 
     // closes the current epoch, flushing if needed, shutting if needed, and updating the frontier.
     fn close_epoch(&mut self) {
-        if !self.buffer1.is_empty() { self.flush(); }
+        if !self.buffer1.is_empty() {
+            self.flush();
+            self.buffer1 = Vec::new();
+            self.buffer2 = Vec::new();
+        }
         for pusher in self.pushers.iter_mut() {
             pusher.done();
         }
@@ -305,6 +309,9 @@ impl<T:Timestamp, D: Data> Handle<T, D> {
     /// Sends one record into the corresponding timely dataflow `Stream`, at the current epoch.
     pub fn send(&mut self, data: D) {
         // assert!(self.buffer1.capacity() == Message::<T, D>::default_length());
+        if self.buffer1.capacity() == 0 {
+            self.buffer1 = Vec::with_capacity(Message::<T, D>::default_length());
+        }
         self.buffer1.push(data);
         if self.buffer1.len() == self.buffer1.capacity() {
             self.flush();