diff --git a/src/event/modules/ngx_iocp_module.c b/src/event/modules/ngx_iocp_module.c
index 787e22d80..75c5a517b 100644
--- a/src/event/modules/ngx_iocp_module.c
+++ b/src/event/modules/ngx_iocp_module.c
@@ -247,7 +247,7 @@ ngx_int_t ngx_iocp_process_events(ngx_cycle_t *cycle, ngx_msec_t timer,
 
     ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0, "iocp timer: %M", timer);
 
-    rc = GetQueuedCompletionStatus(iocp, &bytes, (LPDWORD) &key,
+    rc = GetQueuedCompletionStatus(iocp, &bytes, (PULONG_PTR) &key,
                                    (LPOVERLAPPED *) &ovlp, (u_long) timer);
 
     if (rc == 0) {