diff --git a/cat.nasm b/cat.nasm
index 74daf88..5fbd559 100644
--- a/cat.nasm
+++ b/cat.nasm
@@ -1,3 +1,4 @@
+;; -*- mode: asm; -*-
 %define SYS_open 0x2
 %define SYS_close 0x3
 %define SYS_write 0x1