diff --git a/desCode.h b/desCode.h
index d27df606d82b111a8abcbb84351aa9084f653f2f..524695212fd99c21dbdb181e354546b31297567e 100644
--- a/desCode.h
+++ b/desCode.h
@@ -9,8 +9,8 @@
 
 #include "des.h"
 
-extern uint32_t des_keymap[];
-extern uint32_t des_bigmap[];
+extern const uint32_t des_keymap[];
+extern const uint32_t des_bigmap[];
 
 /* optional customization:
  * the idea here is to alter the code so it will still run correctly