diff --git a/artiq-fast/windows/build.nix b/artiq-fast/windows/build.nix
index e4652f1..35b5bb1 100644
--- a/artiq-fast/windows/build.nix
+++ b/artiq-fast/windows/build.nix
@@ -28,7 +28,7 @@ win.makeWindowsImage {
   };
 
   # Build install script & skip building iso
-  impureMode = true;
+  impureMode = false;
 
   # impureShellCommands = [
   #   "powershell.exe echo Hello"