diff --git a/ze/theia-slim/Dockerfile b/ze/theia-slim/Dockerfile
index 5aab3cd..f65b198 100644
--- a/ze/theia-slim/Dockerfile
+++ b/ze/theia-slim/Dockerfile
@@ -14,10 +14,7 @@ WORKDIR /home/theia
 ADD buildPackageJson.js ./buildPackageJson.js
 RUN node --experimental-fetch buildPackageJson.js ${THEIA_VERSION} > package.json
 ARG GITHUB_TOKEN
-
-# First yarn generates the lockfile, second one installs things. Don't ask why this is necessary, I don't know either -_-
-RUN yarn && \ 
-    yarn && \
+RUN yarn --pure-lockfile \
     NODE_OPTIONS="--max_old_space_size=4096" yarn theia build && \
     yarn theia download:plugins && \
     yarn --production && \
@@ -26,8 +23,7 @@ RUN yarn && \
     echo *.ts.map >> .yarnclean && \
     echo *.spec.* >> .yarnclean && \
     yarn autoclean --force && \
-    yarn cache clean && \
-    rm -f yarn.lock
+    yarn cache clean
 # Uncomment the following lines to install Zowe Explorer in the container
 # ARG ZOWE_EXPLORER_VERSION=2.9.2
 # RUN cd /home/theia/plugins && \