diff --git a/cfg/gnu.cfg b/cfg/gnu.cfg
index 14d9e0af5..4e1de412f 100644
--- a/cfg/gnu.cfg
+++ b/cfg/gnu.cfg
@@ -1391,4 +1391,8 @@
   <define name="SIGIO" value="29"/>
   <define name="SIGPWR" value="30"/>
   <define name="SIGUNUSED" value="31"/>
+  <!-- see https://man7.org/linux/man-pages/man3/stdin.3.html -->
+  <define name="STDIN_FILENO" value="0"/>
+  <define name="STDOUT_FILENO" value="1"/>
+  <define name="STDERR_FILENO" value="2"/>
 </def>