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