diff --git a/library/ssl_cache.c b/library/ssl_cache.c
index 3677e5153..6ef1a972c 100644
--- a/library/ssl_cache.c
+++ b/library/ssl_cache.c
@@ -300,7 +300,7 @@ int mbedtls_ssl_cache_set( void *data,
     if( ret != 0 )
         goto exit;
 
-    if( session_id_len > 32 )
+    if( session_id_len > sizeof( cur->session_id ) )
     {
         ret = 1;
         goto exit;