diff --git a/source/vibe/core/net.d b/source/vibe/core/net.d
index 63e3a2f..bc1fd75 100644
--- a/source/vibe/core/net.d
+++ b/source/vibe/core/net.d
@@ -53,10 +53,9 @@ NetworkAddress resolveHost(string host, ushort address_family, bool use_dns = tr
 		enforce(use_dns, "Malformed IP address string.");
 		NetworkAddress res;
 		bool success = false;
-		Waitable!(
+		Waitable!(DNSLookupCallback,
 			cb => eventDriver.dns.lookupHost(host, cb),
 			(cb, id) => eventDriver.dns.cancelLookup(id),
-			DNSLookupCallback,
 			(DNSLookupID, DNSStatus status, scope RefAddress[] addrs) {
 				if (status == DNSStatus.ok && addrs.length > 0) {
 					try res = NetworkAddress(addrs[0]);
@@ -473,10 +472,9 @@ mixin(tracer);
 		if (m_context.readBuffer.length > 0) return true;
 		auto mode = timeout <= 0.seconds ? IOMode.immediate : IOMode.once;
 
-		Waitable!(
+		Waitable!(IOCallback,
 			cb => eventDriver.sockets.read(m_socket, m_context.readBuffer.peekDst(), mode, cb),
-			cb => eventDriver.sockets.cancelRead(m_socket),
-			IOCallback
+			cb => eventDriver.sockets.cancelRead(m_socket)
 		) waiter;
 
 		asyncAwaitAny!true(timeout, waiter);
@@ -718,10 +716,9 @@ struct UDPConnection {
 		IOStatus status;
 		size_t nbytes;
 
-		Waitable!(
+		Waitable!(DatagramIOCallback,
 			cb => eventDriver.sockets.send(m_socket, data, IOMode.once, addrc, cb),
 			cb => eventDriver.sockets.cancelSend(m_socket),
-			DatagramIOCallback,
 			(DatagramSocketFD, IOStatus status_, size_t nbytes_, scope RefAddress addr)
 			{
 				status = status_;
@@ -755,10 +752,9 @@ struct UDPConnection {
 		IOStatus status;
 		size_t nbytes;
 
-		Waitable!(
+		Waitable!(DatagramIOCallback,
 			cb => eventDriver.sockets.receive(m_socket, buf, IOMode.once, cb),
 			cb => eventDriver.sockets.cancelReceive(m_socket),
-			DatagramIOCallback,
 			(DatagramSocketFD, IOStatus status_, size_t nbytes_, scope RefAddress addr)
 			{
 				status = status_;
diff --git a/source/vibe/core/sync.d b/source/vibe/core/sync.d
index 27138ac..411bd07 100644
--- a/source/vibe/core/sync.d
+++ b/source/vibe/core/sync.d
@@ -1091,10 +1091,9 @@ private struct ThreadLocalWaiter {
 			target_timeout = now + timeout;
 		}
 
-		Waitable!(
+		Waitable!(typeof(Waiter.notifier),
 			cb => w.wait(cb),
 			cb => w.cancel(),
-			typeof(Waiter.notifier)
 		) waitable;
 
 		void removeWaiter()
@@ -1114,7 +1113,7 @@ private struct ThreadLocalWaiter {
 		scope (failure) removeWaiter();
 
 		if (evt != EventID.invalid) {
-			Waitable!(
+			Waitable!(EventCallback,
 				(cb) {
 					eventDriver.events.wait(evt, cb);
 					// check for exit codition *after* starting to wait for the event
@@ -1124,8 +1123,7 @@ private struct ThreadLocalWaiter {
 						cb(evt);
 					}
 				},
-				cb => eventDriver.events.cancelWait(evt, cb),
-				EventCallback
+				cb => eventDriver.events.cancelWait(evt, cb)
 			) ewaitable;
 			asyncAwaitAny!interruptible(timeout, waitable, ewaitable);
 		} else {
diff --git a/source/vibe/internal/async.d b/source/vibe/internal/async.d
index 5734b4c..e2f562f 100644
--- a/source/vibe/internal/async.d
+++ b/source/vibe/internal/async.d
@@ -10,14 +10,14 @@ import core.time : Duration, seconds;
 
 auto asyncAwait(Callback, alias action, alias cancel, string func = __FUNCTION__)()
 if (!is(Object == Duration)) {
-	Waitable!(action, cancel, Callback) waitable;
+	Waitable!(Callback, action, cancel) waitable;
 	asyncAwaitAny!(true, func)(waitable);
 	return tuple(waitable.results);
 }
 
 auto asyncAwait(Callback, alias action, alias cancel, string func = __FUNCTION__)(Duration timeout)
 {
-	Waitable!(action, cancel, Callback) waitable;
+	Waitable!(Callback, action, cancel) waitable;
 	asyncAwaitAny!(true, func)(timeout, waitable);
 	static struct R {
 		bool completed;
@@ -30,19 +30,19 @@ auto asyncAwaitUninterruptible(Callback, alias action, string func = __FUNCTION_
 nothrow {
 	static if (is(typeof(action(Callback.init)) == void)) void cancel(Callback) { assert(false, "Action cannot be cancelled."); }
 	else void cancel(Callback, typeof(action(Callback.init))) { assert(false, "Action cannot be cancelled."); }
-	Waitable!(action, cancel, Callback) waitable;
+	Waitable!(Callback, action, cancel) waitable;
 	asyncAwaitAny!(false, func)(waitable);
 	return tuple(waitable.results);
 }
 
 auto asyncAwaitUninterruptible(Callback, alias action, alias cancel, string func = __FUNCTION__)(Duration timeout)
 nothrow {
-	Waitable!(action, cancel, Callback) waitable;
+	Waitable!(Callback, action, cancel) waitable;
 	asyncAwaitAny!(false, func)(timeout, waitable);
 	return tuple(waitable.results);
 }
 
-struct Waitable(alias wait, alias cancel, CB, on_result...)
+struct Waitable(CB, alias wait, alias cancel, on_result...)
 	if (on_result.length <= 1)
 {
 	import std.traits : ReturnType;
@@ -77,10 +77,9 @@ void asyncAwaitAny(bool interruptible, string func = __FUNCTION__, Waitables...)
 		auto tm = eventDriver.timers.create();
 		eventDriver.timers.set(tm, timeout, 0.seconds);
 		scope (exit) eventDriver.timers.releaseRef(tm);
-		Waitable!(
+		Waitable!(TimerCallback,
 			cb => eventDriver.timers.wait(tm, cb),
-			cb => eventDriver.timers.cancelWait(tm),
-			TimerCallback
+			cb => eventDriver.timers.cancelWait(tm)
 		) timerwaitable;
 		asyncAwaitAny!(interruptible, func)(timerwaitable, waitables);
 	}
@@ -188,19 +187,19 @@ private struct ScopeGuard { @safe nothrow: void delegate() op; ~this() { if (op
 @safe nothrow /*@nogc*/ unittest {
 	int a, b, c;
 	Waitable!(
+		void delegate(int) @safe nothrow,
 		(cb) { a++; cb(42); },
-		(cb) { assert(false); },
-		void delegate(int) @safe nothrow
+		(cb) { assert(false); }
 	) w1;
 	Waitable!(
+		void delegate(int) @safe nothrow,
 		(cb) { b++; },
-		(cb) { c++; },
-		void delegate(int) @safe nothrow
+		(cb) { c++; }
 	) w2;
 	Waitable!(
+		void delegate(int) @safe nothrow,
 		(cb) { c++; cb(42); },
 		(cb) { assert(false); },
-		void delegate(int) @safe nothrow,
 		(int n) { assert(n == 42); }
 	) w3;