diff --git a/drivers/auth/mbedtls/mbedtls_common.c b/drivers/auth/mbedtls/mbedtls_common.c
index e9aa409..cc57af3 100644
--- a/drivers/auth/mbedtls/mbedtls_common.c
+++ b/drivers/auth/mbedtls/mbedtls_common.c
@@ -15,7 +15,7 @@
  * mbed TLS heap
  */
 #if (TF_MBEDTLS_KEY_ALG_ID == TF_MBEDTLS_ECDSA)
-#define MBEDTLS_HEAP_SIZE		(14*1024)
+#define MBEDTLS_HEAP_SIZE		(13*1024)
 #elif (TF_MBEDTLS_KEY_ALG_ID == TF_MBEDTLS_RSA)
 #define MBEDTLS_HEAP_SIZE		(7*1024)
 #endif