diff --git a/include/common/tbbr/cot_def.h b/include/common/tbbr/cot_def.h
index 6ce7f80c17901ab65e8d847a1faf09f469af3f60..0d2d9acfe5d948e76cc688a514fc443e062c5ee2 100644
--- a/include/common/tbbr/cot_def.h
+++ b/include/common/tbbr/cot_def.h
@@ -35,7 +35,7 @@
 #error "Invalid value for TF_MBEDTLS_KEY_SIZE"
 #endif
 #else /* Only using ECDSA keys. */
-#define PK_DER_LEN                      91
+#define PK_DER_LEN                      92
 #endif
 
 #if TF_MBEDTLS_HASH_ALG_ID == TF_MBEDTLS_SHA256