diff --git a/src/main.rs b/src/main.rs
index 58b5a1e..70ac147 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -12,6 +12,10 @@ use runix::{
 #[derive(Parser, Debug)]
 #[command(version, about)]
 struct Args {
+    /// Enables unfree packages, if not already allowed by the local Nix config
+    #[arg(short = 'u', long, required = false)]
+    allow_unfree: bool,
+
     /// List of packages to include in the shell.
     ///
     /// <package> to implicitly use nixpkgs
@@ -25,16 +29,20 @@ fn preprocess(s: &str) -> Result<Installable, String> {
     Ok(Installable::from(if s.contains('#') {
         s.to_owned()
     } else {
-        format!("nixpkgs#{}", s)
+        format!("nixpkgs#{s}")
     }))
 }
 
 #[tokio::main]
 async fn main() -> Result<(), runix::default::NixCommandLineRunError> {
     let cli = Args::parse();
+    std::env::set_var("NIXPKGS_ALLOW_UNFREE", "1");
+
     Shell {
         flake: FlakeArgs::default(),
-        eval: EvaluationArgs::default(),
+        eval: EvaluationArgs {
+            impure: cli.allow_unfree.into(),
+        },
         source: SourceArgs::default(),
         installables: InstallablesArgs::from(cli.pkgs),
     }