diff --git a/includes/cache.inc b/includes/cache.inc
index 8666874..0de097f 100644
--- a/includes/cache.inc
+++ b/includes/cache.inc
@@ -119,6 +119,9 @@ function cache_get_multiple(array &$cids, $bin = 'cache') {
  *   The data to store in the cache. Complex data types will be automatically
  *   serialized before insertion.
  *   Strings will be stored as plain text and not serialized.
+ *   Note that some storage engines only allow objects a maximum of 1MB in size
+ *   to be stored by default. When caching large arrays or similar, take care
+ *   ensure they do not exceed this size.
  * @param $bin
  *   The cache bin to store the data in. Valid core values are 'cache_block',
  *   'cache_bootstrap', 'cache_field', 'cache_filter', 'cache_form',