diff --git a/source/eventcore/driver.d b/source/eventcore/driver.d
index 41f7a93..4b7c41e 100644
--- a/source/eventcore/driver.d
+++ b/source/eventcore/driver.d
@@ -76,6 +76,7 @@ interface EventDriver {
 	void triggerEvent(EventID event, bool notify_all = true);
 	void triggerEvent(EventID event, bool notify_all = true) shared;
 	void waitForEvent(EventID event, EventCallback on_event);
+	void cancelWaitForEvent(EventID event, EventCallback on_event);
 
 	//
 	// Timers
@@ -174,7 +175,6 @@ enum IOMode {
 enum IOStatus {
 	ok,           /// The data has been transferred normally
 	disconnected, /// The connection was closed before all data could be transterred
-	cancelled,    /// The operation was cancelled manually
 	error,        /// An error occured while transferring the data
 	wouldBlock    /// Returned for `IOMode.immediate` when no data is readily readable/writable
 }
diff --git a/source/eventcore/drivers/posix.d b/source/eventcore/drivers/posix.d
index 44491ec..04a4e66 100644
--- a/source/eventcore/drivers/posix.d
+++ b/source/eventcore/drivers/posix.d
@@ -8,6 +8,7 @@ module eventcore.drivers.posix;
 
 public import eventcore.driver;
 import eventcore.drivers.timer;
+import eventcore.internal.consumablequeue : ConsumableQueue;
 import eventcore.internal.utils;
 
 import std.socket : Address, AddressFamily, UnknownAddress;
@@ -282,7 +283,6 @@ abstract class PosixEventDriver : EventDriver {
 		setNotifyCallback!(EventType.read)(socket, null);
 		with (m_fds[socket]) {
 			readBuffer = null;
-			readCallback(socket, IOStatus.cancelled, bytesRead);
 		}
 	}
 
@@ -378,7 +378,6 @@ abstract class PosixEventDriver : EventDriver {
 		setNotifyCallback!(EventType.write)(socket, null);
 		with (m_fds[socket]) {
 			writeBuffer = null;
-			writeCallback(socket, IOStatus.cancelled, bytesWritten);
 		}
 	}
 
@@ -482,6 +481,7 @@ abstract class PosixEventDriver : EventDriver {
 	{
 		auto id = cast(EventID)eventfd(0, EFD_NONBLOCK);
 		initFD(id);
+		m_fds[id].waiters = new ConsumableQueue!EventCallback; // FIXME: avoid dynamic memory allocation
 		registerFD(id, EventMask.read);
 		startNotify!(EventType.read)(id, &onEvent);
 		return id;
@@ -489,6 +489,7 @@ abstract class PosixEventDriver : EventDriver {
 
 	final override void triggerEvent(EventID event, bool notify_all = true)
 	{
+		assert(event < m_fds.length, "Invalid event ID passed to triggerEvent.");
 		if (notify_all) {
 			foreach (w; m_fds[event].waiters.consume)
 				w(event);
@@ -502,6 +503,7 @@ abstract class PosixEventDriver : EventDriver {
 	shared @trusted {
 		import core.atomic : atomicStore;
 		auto thisus = cast(PosixEventDriver)this;
+		assert(event < thisus.m_fds.length, "Invalid event ID passed to shared triggerEvent.");
 		int one = 1;
 		if (notify_all) atomicStore(thisus.m_fds[event].triggerAll, true);
 		() @trusted { write(event, &one, one.sizeof); } ();
@@ -509,9 +511,19 @@ abstract class PosixEventDriver : EventDriver {
 
 	final override void waitForEvent(EventID event, EventCallback on_event)
 	{
+		assert(event < m_fds.length, "Invalid event ID passed to waitForEvent.");
 		return m_fds[event].waiters.put(on_event);
 	}
 
+	final override void cancelWaitForEvent(EventID event, EventCallback on_event)
+	{
+		import std.algorithm.searching : countUntil;
+		import std.algorithm.mutation : remove;
+
+		auto slot = &m_fds[event];
+		slot.waiters.removePending(on_event);
+	}
+
 	private void onEvent(FD event)
 	@trusted {
 		import core.atomic : cas;
@@ -522,7 +534,7 @@ abstract class PosixEventDriver : EventDriver {
 	final override void addRef(SocketFD fd)
 	{
 		auto pfd = &m_fds[fd];
-		assert(pfd.refCount > 0);
+		assert(pfd.refCount > 0, "Adding reference to unreferenced socket FD.");
 		m_fds[fd].refCount++;
 	}
 
@@ -534,14 +546,14 @@ abstract class PosixEventDriver : EventDriver {
 	final override void addRef(EventID descriptor)
 	{
 		auto pfd = &m_fds[descriptor];
-		assert(pfd.refCount > 0);
+		assert(pfd.refCount > 0, "Adding reference to unreferenced event FD.");
 		m_fds[descriptor].refCount++;
 	}
 
 	final override void releaseRef(SocketFD fd)
 	{
 		auto pfd = &m_fds[fd];
-		assert(pfd.refCount > 0);
+		assert(pfd.refCount > 0, "Releasing reference to unreferenced socket FD.");
 		if (--m_fds[fd].refCount == 0) {
 			unregisterFD(fd);
 			clearFD(fd);
@@ -553,16 +565,11 @@ abstract class PosixEventDriver : EventDriver {
 	{
 		assert(false);
 	}
-	
-	final override void releaseRef(TimerID descriptor)
-	{
-		assert(false);
-	}
-	
+		
 	final override void releaseRef(EventID descriptor)
 	{
 		auto pfd = &m_fds[descriptor];
-		assert(pfd.refCount > 0);
+		assert(pfd.refCount > 0, "Releasing reference to unreferenced event FD.");
 		if (--m_fds[descriptor].refCount == 0) {
 			unregisterFD(descriptor);
 			clearFD(descriptor);
@@ -627,7 +634,8 @@ import std.stdio : writefln; try writefln("stop notify %s %s", evt, fd); catch(E
 
 	private void setNotifyCallback(EventType evt)(FD fd, FDSlotCallback callback)
 	{
-		assert((callback !is null) != (m_fds[fd].callback[evt] !is null));
+		assert((callback !is null) != (m_fds[fd].callback[evt] !is null),
+			"Overwriting notification callback.");
 		m_fds[fd].callback[evt] = callback;
 	}
 
@@ -649,6 +657,10 @@ import std.stdio : writefln; try writefln("stop notify %s %s", evt, fd); catch(E
 	{
 		if (m_fds[fd].userDataDestructor)
 			() @trusted { m_fds[fd].userDataDestructor(m_fds[fd].userData.ptr); } ();
+		() @trusted nothrow {
+			scope (failure) assert(false);
+			destroy(m_fds[fd].waiters);
+		} ();
 		m_fds[fd] = FDSlot.init;
 	}
 }
@@ -658,8 +670,6 @@ alias FDEnumerateCallback = void delegate(FD);
 alias FDSlotCallback = void delegate(FD);
 
 private struct FDSlot {
-	import eventcore.internal.consumablequeue;
-
 	FDSlotCallback[EventType.max+1] callback;
 
 	uint refCount;