diff --git a/src/dockerfile.ts b/src/dockerfile.ts
index 457ccba4..ca020d88 100644
--- a/src/dockerfile.ts
+++ b/src/dockerfile.ts
@@ -34,7 +34,7 @@ export const language = <ILanguage>{
 	defaultToken: '',
 	tokenPostfix: '.dockerfile',
 
-	instructions: /FROM|MAINTAINER|RUN|EXPOSE|ENV|ADD|VOLUME|LABEL|USER|WORKDIR|COPY|CMD|STOPSIGNAL|SHELL|HEALTHCHECK|ENTRYPOINT/,
+	instructions: /FROM|MAINTAINER|RUN|EXPOSE|ENV|ADD|ARG|VOLUME|LABEL|USER|WORKDIR|COPY|CMD|STOPSIGNAL|SHELL|HEALTHCHECK|ENTRYPOINT/,
 
 	instructionAfter: /ONBUILD/,