diff --git a/README.md b/README.md
index a715ca9..b47258f 100644
--- a/README.md
+++ b/README.md
@@ -32,6 +32,8 @@ You can also build the docs using docker:
     #   ./doc/build/latex/kompetenzinventar.pdf
     #   ./doc/build/singlehtml/
 
+Warning: the builder uses the `sphinx-latexpdf` base image, which contains an entire texlive environment, making it very large (~2.9G).
+
 ## Roadmap
 
 See the [open issues](https://github.com/github_username/repo_name/issues) for a list of proposed features (and known issues).