diff --git a/post_build/README.experimental_steamclient.md b/post_build/README.experimental_steamclient.md
index 0e64e5cb..3a4b3129 100644
--- a/post_build/README.experimental_steamclient.md
+++ b/post_build/README.experimental_steamclient.md
@@ -93,3 +93,6 @@ New value:      <FOLDER CONTAINING THE LOADER>
 ```
 
 This affects source-engine mods  
+
+## Linux
+On Linux, you may need to set the environment variable `PROTON_DISABLE_LSTEAMCLIENT=1` when running `steamclient_loader.exe`, depending on the Proton variant you are using (e.g. Proton GE run through Lutris or UMU needs it).
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