diff --git a/library/ssl_cookie.c b/library/ssl_cookie.c
index 4bf9058..323784c 100644
--- a/library/ssl_cookie.c
+++ b/library/ssl_cookie.c
@@ -134,8 +134,7 @@
 {
     unsigned char hmac_out[COOKIE_MD_OUTLEN];
 
-    if( (size_t)( end - *p ) < COOKIE_HMAC_LEN )
-        return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
+    MBEDTLS_SSL_CHK_BUF_PTR( *p, end, COOKIE_HMAC_LEN );
 
     if( mbedtls_md_hmac_reset(  hmac_ctx ) != 0 ||
         mbedtls_md_hmac_update( hmac_ctx, time, 4 ) != 0 ||
@@ -165,8 +164,7 @@
     if( ctx == NULL || cli_id == NULL )
         return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
 
-    if( (size_t)( end - *p ) < COOKIE_LEN )
-        return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
+    MBEDTLS_SSL_CHK_BUF_PTR( *p, end, COOKIE_LEN );
 
 #if defined(MBEDTLS_HAVE_TIME)
     t = (unsigned long) mbedtls_time( NULL );