diff --git a/include/ntapi/nt_socket.h b/include/ntapi/nt_socket.h
index 35d6e34..bcb1722 100644
--- a/include/ntapi/nt_socket.h
+++ b/include/ntapi/nt_socket.h
@@ -192,11 +192,6 @@
 #define NT_AFD_DISCONNECT_WR	(0x01u)
 #define NT_AFD_DISCONNECT_RD	(0x02u)
 
-/* socket portable shutdown options */
-#define NT_SHUT_RD		(0x00u)
-#define NT_SHUT_WR		(0x01u)
-#define NT_SHUT_RDWR		(0x02u)
-
 /* send, sendto, sendmsg: *nix flags and bit place-holders */
 #define NT_MSG_OOB		(0x00000001u)
 #define NT_MSG_PEEK		(0x00000002u)
@@ -403,8 +398,7 @@ typedef int32_t __cdecl ntapi_sc_recv(
 
 typedef int32_t __cdecl ntapi_sc_shutdown(
 	__in	nt_socket *		hssocket,
-	__in	uintptr_t		psxhow,
-	__in	uintptr_t		afdhow,
+	__in	uint32_t		afdhow,
 	__out	nt_io_status_block *	iosb	__optional);
 
 
diff --git a/src/socket/ntapi_sc_shutdown.c b/src/socket/ntapi_sc_shutdown.c
index 0aa5c36..acbc09b 100644
--- a/src/socket/ntapi_sc_shutdown.c
+++ b/src/socket/ntapi_sc_shutdown.c
@@ -13,8 +13,7 @@
 
 int32_t __cdecl __ntapi_sc_shutdown(
 	__in	nt_socket *		hssocket,
-	__in	uintptr_t		psxhow,
-	__in	uintptr_t		afdhow,
+	__in	uint32_t		afdhow,
 	__out	nt_io_status_block *	iosb	__optional)
 {
 	nt_afd_disconnect_info	afd_disconnect;
@@ -22,27 +21,10 @@ int32_t __cdecl __ntapi_sc_shutdown(
 
 	iosb = iosb ? iosb : &siosb;
 
-	if (afdhow == 0) {
-		switch (psxhow) {
-			case NT_SHUT_RD:
-				afdhow = NT_AFD_DISCONNECT_RD;
-				break;
+	if (afdhow & ~(NT_AFD_DISCONNECT_RD | NT_AFD_DISCONNECT_WR))
+		return NT_STATUS_INVALID_PARAMETER;
 
-			case NT_SHUT_WR:
-				afdhow = NT_AFD_DISCONNECT_WR;
-				break;
-
-			case NT_SHUT_RDWR:
-				afdhow = NT_AFD_DISCONNECT_RD | NT_AFD_DISCONNECT_WR;
-				break;
-
-			default:
-				return NT_STATUS_INVALID_PARAMETER_2;
-				break;
-		}
-	}
-
-	afd_disconnect.shutdown_flags = (uint32_t)afdhow;
+	afd_disconnect.shutdown_flags = afdhow;
 	afd_disconnect.unknown[0] = 0xff;
 	afd_disconnect.unknown[1] = 0xff;
 	afd_disconnect.unknown[2] = 0xff;