diff --git a/io.c b/io.c
index 1e5c851f87..314bd57452 100644
--- a/io.c
+++ b/io.c
@@ -1577,13 +1577,13 @@ rb_wait_for_single_fd(int fd, int events, struct timeval *timeout)
 int
 rb_thread_wait_fd(int fd)
 {
-    return rb_wait_for_single_fd(fd, RUBY_IO_READABLE, NULL);
+    return io_wait_for_single_fd(fd, RUBY_IO_READABLE, NULL);
 }
 
 int
 rb_thread_fd_writable(int fd)
 {
-    return rb_wait_for_single_fd(fd, RUBY_IO_WRITABLE, NULL);
+    return io_wait_for_single_fd(fd, RUBY_IO_WRITABLE, NULL);
 }
 
 VALUE