diff --git a/library/des.c b/library/des.c
index 09f95cf..863a80c 100644
--- a/library/des.c
+++ b/library/des.c
@@ -34,6 +34,7 @@
 #if defined(MBEDTLS_DES_C)
 
 #include "mbedtls/des.h"
+#include "mbedtls/utils.h"
 
 #include <string.h>
 
@@ -48,11 +49,6 @@
 
 #if !defined(MBEDTLS_DES_ALT)
 
-/* Implementation that should never be optimized out by the compiler */
-static void mbedtls_zeroize( void *v, size_t n ) {
-    volatile unsigned char *p = (unsigned char*)v; while( n-- ) *p++ = 0;
-}
-
 /*
  * 32-bit integer manipulation macros (big endian)
  */