diff --git a/src/ejabberd_config.erl b/src/ejabberd_config.erl
index 8b55be2db..c7849792b 100644
--- a/src/ejabberd_config.erl
+++ b/src/ejabberd_config.erl
@@ -68,6 +68,10 @@
 
 -optional_callbacks([globals/0]).
 
+-ifndef(OTP_BELOW_28).
+-dialyzer([no_opaque_union]).
+-endif.
+
 %%%===================================================================
 %%% API
 %%%===================================================================
diff --git a/src/ejabberd_shaper.erl b/src/ejabberd_shaper.erl
index c47d72dbd..af0b3faba 100644
--- a/src/ejabberd_shaper.erl
+++ b/src/ejabberd_shaper.erl
@@ -36,6 +36,10 @@
 
 -export_type([shaper/0, shaper_rule/0, shaper_rate/0]).
 
+-ifndef(OTP_BELOW_28).
+-dialyzer([no_opaque_union]).
+-endif.
+
 %%%===================================================================
 %%% API
 %%%===================================================================
diff --git a/src/ejabberd_websocket.erl b/src/ejabberd_websocket.erl
index 43b6673d4..dbcf8e2e0 100644
--- a/src/ejabberd_websocket.erl
+++ b/src/ejabberd_websocket.erl
@@ -62,6 +62,11 @@
                           ?AC_ALLOW_HEADERS, ?AC_MAX_AGE]).
 -define(HEADER, [?CT_XML, ?AC_ALLOW_ORIGIN, ?AC_ALLOW_HEADERS]).
 
+-ifndef(OTP_BELOW_28).
+-dialyzer([no_opaque_union]).
+-endif.
+
+
 is_valid_websocket_upgrade(_Path, Headers) ->
     HeadersToValidate = [{'Upgrade', <<"websocket">>},
                          {'Connection', ignore},
diff --git a/src/mod_muc_room.erl b/src/mod_muc_room.erl
index f9fb9f882..f48e58a94 100644
--- a/src/mod_muc_room.erl
+++ b/src/mod_muc_room.erl
@@ -116,6 +116,10 @@
 -callback search_affiliation(binary(), binary(), binary(), affiliation()) ->
     {ok, [{ljid(), {affiliation(), binary()}}]} | {error, any()}.
 
+-ifndef(OTP_BELOW_28).
+-dialyzer([no_opaque_union]).
+-endif.
+
 %%%----------------------------------------------------------------------
 %%% API
 %%%----------------------------------------------------------------------