diff --git a/examples/playback_capture.rs b/examples/playback_capture.rs
index 6a1e8ee9..9f2f4cef 100644
--- a/examples/playback_capture.rs
+++ b/examples/playback_capture.rs
@@ -64,11 +64,6 @@ impl jack::NotificationHandler for Notifications {
         );
     }
 
-    fn buffer_size(&mut self, _: &jack::Client, sz: jack::Frames) -> jack::Control {
-        println!("JACK: buffer size changed to {}", sz);
-        jack::Control::Continue
-    }
-
     fn sample_rate(&mut self, _: &jack::Client, srate: jack::Frames) -> jack::Control {
         println!("JACK: sample rate changed to {}", srate);
         jack::Control::Continue
diff --git a/src/client/callbacks.rs b/src/client/callbacks.rs
index d5cb276d..baf72666 100644
--- a/src/client/callbacks.rs
+++ b/src/client/callbacks.rs
@@ -25,12 +25,6 @@ pub trait NotificationHandler: Send {
     /// Called whenever "freewheel" mode is entered or leaving.
     fn freewheel(&mut self, _: &Client, _is_freewheel_enabled: bool) {}
 
-    /// Called whenever the size of the buffer that will be passed to `process`
-    /// is about to change.
-    fn buffer_size(&mut self, _: &Client, _size: Frames) -> Control {
-        Control::Continue
-    }
-
     /// Called whenever the system sample rate changes.
     fn sample_rate(&mut self, _: &Client, _srate: Frames) -> Control {
         Control::Continue
@@ -150,6 +144,16 @@ pub trait ProcessHandler: Send {
     /// Should return `Control::Continue` on success, and
     /// `Control::Quit` on error.
     fn process(&mut self, _: &Client, _process_scope: &ProcessScope) -> Control;
+    
+    /// Called whenever the size of the buffer that will be passed to `process`
+    /// is about to change, and once before the first call to `process`.
+    ///
+    /// It is called on the same thread as `process`, but as an exception, does
+    /// not need to be suitable for real-time execution, so it is allowed to
+    /// allocate new buffers to accomodate the buffer size for example.
+    fn buffer_size(&mut self, _: &Client, _size: Frames) -> Control {
+        Control::Continue
+    }
 }
 
 unsafe extern "C" fn thread_init_callback<N, P>(data: *mut libc::c_void)
@@ -210,7 +214,7 @@ where
     P: 'static + Send + ProcessHandler,
 {
     let ctx = CallbackContext::<N, P>::from_raw(data);
-    ctx.notification.buffer_size(&ctx.client, n_frames).to_ffi()
+    ctx.process.buffer_size(&ctx.client, n_frames).to_ffi()
 }
 
 unsafe extern "C" fn sample_rate<N, P>(n_frames: Frames, data: *mut libc::c_void) -> libc::c_int
diff --git a/src/client/test_callback.rs b/src/client/test_callback.rs
index a42040c5..b619cee2 100644
--- a/src/client/test_callback.rs
+++ b/src/client/test_callback.rs
@@ -27,11 +27,6 @@ impl NotificationHandler for Counter {
         self.thread_init_count.fetch_add(1, Ordering::Relaxed);
     }
 
-    fn buffer_size(&mut self, _: &Client, size: Frames) -> Control {
-        self.buffer_size_change_history.push(size);
-        Control::Continue
-    }
-
     fn client_registration(&mut self, _: &Client, name: &str, is_registered: bool) {
         if is_registered {
             self.registered_client_history.push(name.to_string())
@@ -65,6 +60,11 @@ impl ProcessHandler for Counter {
         }
         Control::Continue
     }
+
+    fn buffer_size(&mut self, _: &Client, size: Frames) -> Control {
+        self.buffer_size_change_history.push(size);
+        Control::Continue
+    }
 }
 
 fn open_test_client(name: &str) -> Client {