diff --git a/include/mbedtls/cmac.h b/include/mbedtls/cmac.h
index a7f7f45..1cac948 100644
--- a/include/mbedtls/cmac.h
+++ b/include/mbedtls/cmac.h
@@ -31,6 +31,8 @@
 extern "C" {
 #endif
 
+#define MBEDTLS_ERR_CMAC_HW_ACCEL_FAILED                  -0x007A  /**< CMAC hardware accelerator failed. */
+
 #define MBEDTLS_AES_BLOCK_SIZE          16
 #define MBEDTLS_DES3_BLOCK_SIZE         8