diff --git a/lib/make-hpc-dist/default.nix b/lib/make-hpc-dist/default.nix
index b7cc2e4..233c1fd 100644
--- a/lib/make-hpc-dist/default.nix
+++ b/lib/make-hpc-dist/default.nix
@@ -82,7 +82,7 @@ let
   '';
 
 
-  squashfs = makeSquashFs { filename = "nix-store"; storeContents = [ shell ]; };
+  squashfs = makeSquashFs { filename = "nix-store"; storeContents = [ shell ]; comp = "gzip -9"; };
 
   startCommand = writeText "run-container.sh" ''
     #!/usr/bin/env bash