diff --git a/boot/bootutil/src/image_ec256.c b/boot/bootutil/src/image_ec256.c
index 185624c..f5b8135 100644
--- a/boot/bootutil/src/image_ec256.c
+++ b/boot/bootutil/src/image_ec256.c
@@ -30,6 +30,9 @@
 
 #ifdef MCUBOOT_SIGN_EC256
 /*TODO: remove this after cypress port mbedtls to abstract crypto api */
+#ifdef MCUBOOT_USE_CC310
+#define NUM_ECC_BYTES (256 / 8)
+#endif
 #if defined (MCUBOOT_USE_TINYCRYPT) || defined (MCUBOOT_USE_CC310)
 #include "bootutil/sign_key.h"