diff --git a/tests/server/sockfilt.c b/tests/server/sockfilt.c
index 5e57b193e9..8cc9b877d5 100644
--- a/tests/server/sockfilt.c
+++ b/tests/server/sockfilt.c
@@ -413,8 +413,8 @@ struct select_ws_wait_data {
   HANDLE abort;  /* internal event to abort waiting threads */
 };
 #include <process.h>
-static
-unsigned int CURL_WIN_THREADFUNC select_ws_wait_thread(void *lpParameter)
+static CURL_THREAD_RETURN_T
+CURL_WIN_THREADFUNC select_ws_wait_thread(void *lpParameter)
 {
   struct select_ws_wait_data *data;
   HANDLE signal, handle, handles[2];