diff --git a/Dockerfile b/Dockerfile
index ebc874b..c50c0f3 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -32,7 +32,7 @@ RUN chmod 755 /usr/local/bin/geminabox
 # https://github.com/rubygems/rubygems/issues/2918
 # https://gitlab.alpinelinux.org/alpine/aports/issues/10808
 COPY ./rubygems-platform-musl.patch /tmp/
-RUN patch -d /usr/lib/ruby/2.5.0 -Np 0 -i /tmp/rubygems-platform-musl.patch
+RUN cd /usr/lib/ruby/2.5.0 && patch -Np 0 -i /tmp/rubygems-platform-musl.patch
 
 EXPOSE 9292
 VOLUME /srv/gems