diff --git a/bn_mp_to_radix.c b/bn_mp_to_radix.c
index d6e8fcc..6e99777 100644
--- a/bn_mp_to_radix.c
+++ b/bn_mp_to_radix.c
@@ -1,5 +1,5 @@
 #include "tommath_private.h"
-#ifdef BN_MP_TORADIX_N_C
+#ifdef BN_MP_TO_RADIX_C
 /* LibTomMath, multiple-precision integer library -- Tom St Denis */
 /* SPDX-License-Identifier: Unlicense */