diff --git a/include/ejabberd_commands.hrl b/include/ejabberd_commands.hrl
index d939f3c3d..a6a960d8c 100644
--- a/include/ejabberd_commands.hrl
+++ b/include/ejabberd_commands.hrl
@@ -19,13 +19,18 @@
 %%%----------------------------------------------------------------------
 
 -type aterm() :: {atom(), atype()}.
--type atype() :: integer | string | binary |
+-type atype() :: integer | string | binary | any | atom |
                  {tuple, [aterm()]} | {list, aterm()}.
 -type rterm() :: {atom(), rtype()}.
--type rtype() :: integer | string | atom |
+-type rtype() :: integer | string | atom | any |
                  {tuple, [rterm()]} | {list, rterm()} |
                  rescode | restuple.
 
+%% The 'any' and 'atom' argument types and 'any' result type
+%% should only be used %% by commands with tag 'internal',
+%% which are meant to be used only internally in ejabberd,
+%% and not called using external frontends.
+
 %% The purpose of a command can either be:
 %% - informative: its purpose is to obtain information
 %% - modifier: its purpose is to produce some change in the server
diff --git a/src/ejabberd_ctl.erl b/src/ejabberd_ctl.erl
index 80d942a6d..89adcdcd6 100644
--- a/src/ejabberd_ctl.erl
+++ b/src/ejabberd_ctl.erl
@@ -976,11 +976,14 @@ format_usage_ctype1({Name, Type, Description}, Indentation, ShCode) ->
 
 
 format_usage_ctype(Type, _Indentation)
-  when (Type==atom) or (Type==integer) or (Type==string) or (Type==binary) or (Type==rescode) or (Type==restuple)->
+  when (Type==atom) or (Type==integer) or (Type==string) or (Type==binary)
+       or (Type==rescode) or (Type==restuple) ->
     io_lib:format("~p", [Type]);
 
 format_usage_ctype({Name, Type}, _Indentation)
-  when (Type==atom) or (Type==integer) or (Type==string) or (Type==binary) or (Type==rescode) or (Type==restuple)->
+  when (Type==atom) or (Type==integer) or (Type==string) or (Type==binary)
+       or (Type==rescode) or (Type==restuple)
+       or (Type==any) ->
     io_lib:format("~p::~p", [Name, Type]);
 
 format_usage_ctype({Name, {list, ElementDef}}, Indentation) ->