diff --git a/include/u-boot/ecdsa.h b/include/u-boot/ecdsa.h
index 53490c6..8f9f5e7 100644
--- a/include/u-boot/ecdsa.h
+++ b/include/u-boot/ecdsa.h
@@ -65,5 +65,6 @@
 /** @} */
 
 #define ECDSA256_BYTES	(256 / 8)
+#define ECDSA521_BYTES	((521 + 7) / 8)
 
 #endif