diff --git a/source/eventcore/drivers/winapi/sockets.d b/source/eventcore/drivers/winapi/sockets.d
index 4b59e32..fb31517 100644
--- a/source/eventcore/drivers/winapi/sockets.d
+++ b/source/eventcore/drivers/winapi/sockets.d
@@ -8,6 +8,8 @@ import eventcore.internal.win32;
 import eventcore.internal.utils : AlgebraicChoppedVector, print, nogc_assert;
 import std.socket : Address;
 
+import core.time: Duration;
+
 private enum WM_USER_SOCKET = WM_USER + 1;
 
 
@@ -225,7 +227,8 @@ final class WinAPIEventDriverSockets : EventDriverSockets {
 	{
 		tcp_keepalive opts = tcp_keepalive(1, cast(ulong) idle.total!"msecs"(),
 			cast(ulong) interval.total!"msecs");
-		int result = WSAIoctl(socket, SIO_KEEPALIVE_VALS, &opts, tcp_keepalive.sizeof, null, 0, null, null);
+		int result = WSAIoctl(socket, SIO_KEEPALIVE_VALS, &opts, cast(uint) tcp_keepalive.sizeof,
+			null, 0, null, null, null);
 		if (result != 0)
 		{
 			print("WSAIoctl SIO_KEEPALIVE_VALS returned %d", result);
diff --git a/source/eventcore/internal/win32.d b/source/eventcore/internal/win32.d
index 69c99a3..2662502 100644
--- a/source/eventcore/internal/win32.d
+++ b/source/eventcore/internal/win32.d
@@ -112,18 +112,18 @@ struct tcp_keepalive {
 };
 
 // https://gist.github.com/piscisaureus/906386#file-winsock2-h-L1099
-enum : ulong {
+enum : DWORD {
 	IOC_VENDOR = 0x18000000,
 	IOC_OUT = 0x40000000,
 	IOC_IN = 0x80000000
 }
 
-ulong _WSAIOW(ulong x, ulong y) pure @safe
+DWORD _WSAIOW(DWORD x, DWORD y) pure @safe
 {
 	return IOC_IN | x | y;
 }
 
-enum : ulong {
+enum : DWORD {
 	SIO_KEEPALIVE_VALS = _WSAIOW(IOC_VENDOR, 4)
 }