diff --git a/flake.nix b/flake.nix
index 4da5bde4..1fea70ef 100644
--- a/flake.nix
+++ b/flake.nix
@@ -67,11 +67,11 @@
       };
 
       nixosConfigurations = mkSystem {
-        type = "nixos";
+        isDarwin = false;
       };
 
       darwinConfigurations = mkSystem {
-        type = "darwin";
+        isDarwin = true;
       };
 
       checks = foreachSystem (system: {
diff --git a/lib/default.nix b/lib/default.nix
index 7a77a33b..651afa8b 100644
--- a/lib/default.nix
+++ b/lib/default.nix
@@ -37,10 +37,8 @@ in
       ];
     };
 
-  mkSystem = { type }:
+  mkSystem = { isDarwin }:
     let
-      # TODO: assert type is either "darwin" or "nixos"
-      isDarwin = type == "darwin";
       osConfig = ../system/${if isDarwin then "darwin" else "nixos" };
       hmConfig = ../home;