diff --git a/Dockerfile b/Dockerfile
index d210a61626..3217d5cad2 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -39,4 +39,5 @@ ENV PATH=/home/linuxbrew/.linuxbrew/bin:/home/linuxbrew/.linuxbrew/sbin:$PATH \
 # Install portable-ruby and tap homebrew/core.
 RUN HOMEBREW_NO_ANALYTICS=1 HOMEBREW_NO_AUTO_UPDATE=1 brew tap homebrew/core \
 	&& chown -R linuxbrew: /home/linuxbrew/.linuxbrew \
+	&& chmod -R o-w /home/linuxbrew/.linuxbrew \
 	&& rm -rf ~/.cache