diff --git a/nixos/modules/system/boot/systemd-unit-options.nix b/nixos/modules/system/boot/systemd-unit-options.nix
index 43a9c28bb6940..5255f1a1b97a5 100644
--- a/nixos/modules/system/boot/systemd-unit-options.nix
+++ b/nixos/modules/system/boot/systemd-unit-options.nix
@@ -217,7 +217,7 @@ in rec {
 
     environment = mkOption {
       default = {};
-      type = types.attrs; # FIXME
+      type = with types; attrsOf (nullOr (either str package));
       example = { PATH = "/foo/bar/bin"; LANG = "nl_NL.UTF-8"; };
       description = "Environment variables passed to the service's processes.";
     };
diff --git a/nixos/modules/system/boot/systemd.nix b/nixos/modules/system/boot/systemd.nix
index aff46ea861a2f..87691cbe9e21e 100644
--- a/nixos/modules/system/boot/systemd.nix
+++ b/nixos/modules/system/boot/systemd.nix
@@ -516,7 +516,7 @@ in
     };
 
     systemd.globalEnvironment = mkOption {
-      type = types.attrs;
+      type = with types; attrsOf (nullOr (either str package));
       default = {};
       example = { TZ = "CET"; };
       description = ''