Update runtime files.
diff --git a/runtime/syntax/dockerfile.vim b/runtime/syntax/dockerfile.vim
index 15b6692..4cf50d9 100644
--- a/runtime/syntax/dockerfile.vim
+++ b/runtime/syntax/dockerfile.vim
@@ -1,7 +1,7 @@
" dockerfile.vim - Syntax highlighting for Dockerfiles
" Maintainer: Honza Pokorny <https://honza.ca>
" Version: 0.6
-" Last Change: 2016 Aug 9
+" Last Change: 2019 Aug 16
" License: BSD
@@ -15,6 +15,8 @@
syntax match dockerfileKeyword /\v^\s*(ONBUILD\s+)?(ADD|ARG|CMD|COPY|ENTRYPOINT|ENV|EXPOSE|FROM|HEALTHCHECK|LABEL|MAINTAINER|RUN|SHELL|STOPSIGNAL|USER|VOLUME|WORKDIR)\s/
+syntax match dockerfileKeyword /\v(AS)/
+
syntax region dockerfileString start=/\v"/ skip=/\v\\./ end=/\v"/
syntax match dockerfileComment "\v^\s*#.*$"