diff --git a/library/ccm.c b/library/ccm.c
index 13a8fd1..9101e5f 100644
--- a/library/ccm.c
+++ b/library/ccm.c
@@ -49,6 +49,8 @@
 #endif /* MBEDTLS_PLATFORM_C */
 #endif /* MBEDTLS_SELF_TEST && MBEDTLS_AES_C */
 
+#if !defined(MBEDTLS_CCM_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;
@@ -348,6 +350,7 @@
     return( 0 );
 }
 
+#endif /* !MBEDTLS_CCM_ALT */
 
 #if defined(MBEDTLS_SELF_TEST) && defined(MBEDTLS_AES_C)
 /*