Update runtime files.
diff --git a/runtime/syntax/erlang.vim b/runtime/syntax/erlang.vim
index c65ebf3..b8cbf07 100644
--- a/runtime/syntax/erlang.vim
+++ b/runtime/syntax/erlang.vim
@@ -2,7 +2,7 @@
" Language: Erlang (http://www.erlang.org)
" Maintainer: Csaba Hoch <csaba.hoch@gmail.com>
" Contributor: Adam Rutkowski <hq@mtod.org>
-" Last Update: 2019-Jun-18
+" Last Update: 2020-May-26
" License: Vim license
" URL: https://github.com/vim-erlang/vim-erlang-runtime
@@ -44,7 +44,7 @@
" Comments
syn match erlangComment '%.*$' contains=erlangCommentAnnotation,erlangTodo
-syn match erlangCommentAnnotation ' \@<=@\%(clear\|docfile\|end\|headerfile\|todo\|TODO\|type\|author\|copyright\|doc\|reference\|see\|since\|title\|version\|deprecated\|hidden\|private\|equiv\|spec\|throws\)' contained
+syn match erlangCommentAnnotation ' \@<=@\%(clear\|docfile\|end\|headerfile\|todo\|TODO\|type\|author\|copyright\|doc\|reference\|see\|since\|title\|version\|deprecated\|hidden\|param\|private\|equiv\|spec\|throws\)' contained
syn match erlangCommentAnnotation /`[^']*'/ contained
syn keyword erlangTodo TODO FIXME XXX contained
@@ -92,7 +92,7 @@
" Constants and Directives
syn match erlangUnknownAttribute '^\s*-\%(\s\|\n\|%.*\n\)*\l[[:alnum:]_@]*' contains=erlangComment
-syn match erlangAttribute '^\s*-\%(\s\|\n\|%.*\n\)*\%(behaviou\=r\|compile\|export\(_type\)\=\|file\|import\|module\|author\|copyright\|doc\|vsn\|on_load\)\>' contains=erlangComment
+syn match erlangAttribute '^\s*-\%(\s\|\n\|%.*\n\)*\%(behaviou\=r\|compile\|export\(_type\)\=\|file\|import\|module\|author\|copyright\|doc\|vsn\|on_load\|optional_callbacks\)\>' contains=erlangComment
syn match erlangInclude '^\s*-\%(\s\|\n\|%.*\n\)*\%(include\|include_lib\)\>' contains=erlangComment
syn match erlangRecordDef '^\s*-\%(\s\|\n\|%.*\n\)*record\>' contains=erlangComment
syn match erlangDefine '^\s*-\%(\s\|\n\|%.*\n\)*\%(define\|undef\)\>' contains=erlangComment