diff --git a/doc/lua_api.txt b/doc/lua_api.txt
index 593ab50d..a45466b5 100644
--- a/doc/lua_api.txt
+++ b/doc/lua_api.txt
@@ -1502,6 +1502,7 @@ Special groups
 * `fall_damage_add_percent`: damage speed = `speed * (1 + value/100)`
 * `bouncy`: value is bounce speed in percent
 * `falling_node`: if there is no walkable block under the node it will fall
+* `float`: the node will not fall through liquids
 * `attached_node`: if the node under it is not a walkable block the node will be
   dropped as an item. If the node is wallmounted the wallmounted direction is
   checked.