diff --git a/README.md b/README.md
index a7759b2fc..997498dd3 100644
--- a/README.md
+++ b/README.md
@@ -264,6 +264,10 @@ The Glistix project officially maintains a few ports of core Gleam packages to w
 
 Great job! You now have a basic project up and running. You can **import its modules from Nix** by importing `default.nix` elsewhere (or adding your project's repository as an input to another `flake.nix` elsewhere) and using `lib.loadGlistixPackage { }` (or `{ module = "module/name"; }` to pick a module). You can also cache the build folder in your repository by copying it to `output`, as [described in the previous sections](#build-caching).
 
+> [!WARNING]
+>
+> When in pure evaluation mode (e.g. in Flakes without `--impure`), you will have to specify the system in `package.lib.loadGlistixPackage { system = "system name"; }` (e.g. `"x86_64-linux"`), as the package would have to be built using a Glistix derivation (which depends on the system), **unless the package you're using caches build output** (in which case the system isn't necessary at all, as the Nix files are ready to be imported, so no build occurs).
+
 [Check out the Glistix book](https://glistix.github.io/book/getting-started/basic-usage.html) for more information!
 
 ### Using Glistix within editors / with Gleam LSP