diff --git a/ChangeLog.md b/ChangeLog.md
index 5fa26b3..d56be7a 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,3 +1,6 @@
+# Now
+
+- `perSystem`: Set `systems` argument by default to `nixpkgs.lib.systems.flakeExposed`
 
 # 2022-05-25
 
diff --git a/modules/perSystem.nix b/modules/perSystem.nix
index 1e9be2c..f1f6de1 100644
--- a/modules/perSystem.nix
+++ b/modules/perSystem.nix
@@ -18,6 +18,7 @@ in
     systems = mkOption {
       description = "All the system types to enumerate in the flake.";
       type = types.listOf types.str;
+      default = lib.systems.flakeExposed;
     };
 
     perInput = mkOption {