diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 6ad6f0876..ea8db8c92 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -1675,7 +1675,7 @@ int mbedtls_ssl_encrypt_buf( mbedtls_ssl_context *ssl,
     mbedtls_cipher_mode_t mode;
     int auth_done = 0;
     unsigned char * data;
-    unsigned char add_data[13 + 1 + MBEDTLS_SSL_CID_LEN_MAX ];
+    unsigned char add_data[13 + 1 + MBEDTLS_SSL_CID_OUT_LEN_MAX ];
     size_t add_data_len;
     size_t post_avail;
 
@@ -2115,7 +2115,7 @@ int mbedtls_ssl_decrypt_buf( mbedtls_ssl_context *ssl,
     size_t padlen = 0, correct = 1;
 #endif
     unsigned char* data;
-    unsigned char add_data[13 + 1 + MBEDTLS_SSL_CID_LEN_MAX ];
+    unsigned char add_data[13 + 1 + MBEDTLS_SSL_CID_IN_LEN_MAX ];
     size_t add_data_len;
 
 #if !defined(MBEDTLS_DEBUG_C)