diff --git a/dlls/ws2_32/tests/sock.c b/dlls/ws2_32/tests/sock.c
index 91305f9f01b..137c0f681ef 100644
--- a/dlls/ws2_32/tests/sock.c
+++ b/dlls/ws2_32/tests/sock.c
@@ -6862,7 +6862,7 @@ static DWORD CALLBACK write_watch_thread( void *arg )
 {
     struct write_watch_thread_args *args = arg;
     struct sockaddr addr;
-    int addr_len, ret;
+    int addr_len = sizeof(addr), ret;
     DWORD bytes, flags = 0;
     WSABUF buf[1];