diff --git a/include/mbedtls/cmac.h b/include/mbedtls/cmac.h
index 9a2b96b..4d3f2d2 100644
--- a/include/mbedtls/cmac.h
+++ b/include/mbedtls/cmac.h
@@ -39,6 +39,8 @@
 #define MBEDTLS_CIPHER_BLKSIZE_MAX      8   /* longest used by CMAC is 3DES */
 #endif
 
+#if !defined(MBEDTLS_CMAC_ALT)
+
 /**
  * CMAC context structure - Contains internal state information only
  */
@@ -154,6 +156,18 @@
                               unsigned char output[16] );
 #endif /* MBEDTLS_AES_C */
 
+#ifdef __cplusplus
+}
+#endif
+
+#else  /* !MBEDTLS_CMAC_ALT */
+#include "cmac_alt.h"
+#endif /* !MBEDTLS_CMAC_ALT */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #if defined(MBEDTLS_SELF_TEST) && ( defined(MBEDTLS_AES_C) || defined(MBEDTLS_DES_C) )
 /**
  * \brief          Checkup routine
diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index 0f7e29b..2ef052b 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -237,6 +237,7 @@
 //#define MBEDTLS_ARC4_ALT
 //#define MBEDTLS_BLOWFISH_ALT
 //#define MBEDTLS_CAMELLIA_ALT
+//#define MBEDTLS_CMAC_ALT
 //#define MBEDTLS_DES_ALT
 //#define MBEDTLS_XTEA_ALT
 //#define MBEDTLS_MD2_ALT
diff --git a/library/cmac.c b/library/cmac.c
index b2fe713..5575d5c 100644
--- a/library/cmac.c
+++ b/library/cmac.c
@@ -65,6 +65,8 @@
 #endif /* MBEDTLS_SELF_TEST */
 #endif /* MBEDTLS_PLATFORM_C */
 
+#if !defined(MBEDTLS_CMAC_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;
@@ -468,6 +470,8 @@
 }
 #endif /* MBEDTLS_AES_C */
 
+#endif /* !MBEDTLS_CMAC_ALT */
+
 #if defined(MBEDTLS_SELF_TEST)
 /*
  * CMAC test data for SP800-38B