diff --git a/includes/cache.inc b/includes/cache.inc
index f76164b..913f576 100644
--- a/includes/cache.inc
+++ b/includes/cache.inc
@@ -99,6 +99,9 @@ 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 are
  *   not serialized.
+ *   Some storage engines only allow objects up to a maximum of 1MB in size to
+ *   be stored by default. When caching large arrays or similar, take care to
+ *   ensure $data does not exceed this size.
  * @param $bin
  *   The cache bin to store the data in. Valid core values are:
  *   - cache: (default) Generic cache storage bin (used for theme registry,