diff --git a/stdlib/linux.sl b/stdlib/linux.sl
index c6a8904..9463892 100644
--- a/stdlib/linux.sl
+++ b/stdlib/linux.sl
@@ -3,9 +3,9 @@
 # Linux syscall constants + convenience wrappers for L2
 
 # File descriptor constants
-macro fd_stdin 0 0 ;
-macro fd_stdout 0 1 ;
-macro fd_stderr 0 2 ;
+macro FD_STDIN 0 0 ;
+macro FD_STDOUT 0 1 ;
+macro FD_STDERR 0 2 ;
 
 # Common open(2) flags
 macro O_RDONLY 0 0 ;
diff --git a/tools/gen_linux_sl.py b/tools/gen_linux_sl.py
index 50807c2..4e82b3a 100644
--- a/tools/gen_linux_sl.py
+++ b/tools/gen_linux_sl.py
@@ -65,9 +65,9 @@ def _emit_header(lines: list[str]) -> None:
             "# Linux syscall constants + convenience wrappers for L2",
             "",
             "# File descriptor constants",
-            "macro fd_stdin 0 0 ;",
-            "macro fd_stdout 0 1 ;",
-            "macro fd_stderr 0 2 ;",
+            "macro FD_STDIN 0 0 ;",
+            "macro FD_STDOUT 0 1 ;",
+            "macro FD_STDERR 0 2 ;",
             "",
             "# Common open(2) flags",
             "macro O_RDONLY 0 0 ;",