diff --git a/nixos/lib/systemd-lib.nix b/nixos/lib/systemd-lib.nix
index a472d97f5cc7..27c8b5b04713 100644
--- a/nixos/lib/systemd-lib.nix
+++ b/nixos/lib/systemd-lib.nix
@@ -120,10 +120,15 @@ in rec {
         (if isList value then value else [value]))
         as));
 
-  generateUnits = generateUnits' true;
-
-  generateUnits' = allowCollisions: type: units: upstreamUnits: upstreamWants:
-    pkgs.runCommand "${type}-units"
+  generateUnits = { allowCollisions ? true, type, units, upstreamUnits, upstreamWants, packages ? cfg.packages, package ? cfg.package }:
+    let
+      typeDir = ({
+        system = "system";
+        initrd = "system";
+        user = "user";
+        nspawn = "nspawn";
+      }).${type};
+    in pkgs.runCommand "${type}-units"
       { preferLocalBuild = true;
         allowSubstitutes = false;
       } ''
@@ -131,7 +136,7 @@ in rec {
 
       # Copy the upstream systemd units we're interested in.
       for i in ${toString upstreamUnits}; do
-        fn=${cfg.package}/example/systemd/${type}/$i
+        fn=${package}/example/systemd/${typeDir}/$i
         if ! [ -e $fn ]; then echo "missing $fn"; false; fi
         if [ -L $fn ]; then
           target="$(readlink "$fn")"
@@ -148,7 +153,7 @@ in rec {
       # Copy .wants links, but only those that point to units that
       # we're interested in.
       for i in ${toString upstreamWants}; do
-        fn=${cfg.package}/example/systemd/${type}/$i
+        fn=${package}/example/systemd/${typeDir}/$i
         if ! [ -e $fn ]; then echo "missing $fn"; false; fi
         x=$out/$(basename $fn)
         mkdir $x
@@ -160,14 +165,14 @@ in rec {
       done
 
       # Symlink all units provided listed in systemd.packages.
-      packages="${toString cfg.packages}"
+      packages="${toString packages}"
 
       # Filter duplicate directories
       declare -A unique_packages
       for k in $packages ; do unique_packages[$k]=1 ; done
 
       for i in ''${!unique_packages[@]}; do
-        for fn in $i/etc/systemd/${type}/* $i/lib/systemd/${type}/*; do
+        for fn in $i/etc/systemd/${typeDir}/* $i/lib/systemd/${typeDir}/*; do
           if ! [[ "$fn" =~ .wants$ ]]; then
             if [[ -d "$fn" ]]; then
               targetDir="$out/$(basename "$fn")"
diff --git a/nixos/modules/system/boot/systemd.nix b/nixos/modules/system/boot/systemd.nix
index 396457e1a9f9..00116c73ccc6 100644
--- a/nixos/modules/system/boot/systemd.nix
+++ b/nixos/modules/system/boot/systemd.nix
@@ -461,7 +461,12 @@ in
       enabledUpstreamSystemUnits = filter (n: ! elem n cfg.suppressedSystemUnits) upstreamSystemUnits;
       enabledUnits = filterAttrs (n: v: ! elem n cfg.suppressedSystemUnits) cfg.units;
     in ({
-      "systemd/system".source = generateUnits "system" enabledUnits enabledUpstreamSystemUnits upstreamSystemWants;
+      "systemd/system".source = generateUnits {
+        type = "system";
+        units = enabledUnits;
+        upstreamUnits = enabledUpstreamSystemUnits;
+        upstreamWants = upstreamSystemWants;
+      };
 
       "systemd/system.conf".text = ''
         [Manager]
diff --git a/nixos/modules/system/boot/systemd/nspawn.nix b/nixos/modules/system/boot/systemd/nspawn.nix
index 0c6822319a5b..bf9995d03cc1 100644
--- a/nixos/modules/system/boot/systemd/nspawn.nix
+++ b/nixos/modules/system/boot/systemd/nspawn.nix
@@ -116,7 +116,13 @@ in {
     in
       mkMerge [
         (mkIf (cfg != {}) {
-          environment.etc."systemd/nspawn".source = mkIf (cfg != {}) (generateUnits' false "nspawn" units [] []);
+          environment.etc."systemd/nspawn".source = mkIf (cfg != {}) (generateUnits {
+            allowCollisions = false;
+            type = "nspawn";
+            inherit units;
+            upstreamUnits = [];
+            upstreamWants = [];
+          });
         })
         {
           systemd.targets.multi-user.wants = [ "machines.target" ];
diff --git a/nixos/modules/system/boot/systemd/user.nix b/nixos/modules/system/boot/systemd/user.nix
index 82bad43e9f44..4951aef95584 100644
--- a/nixos/modules/system/boot/systemd/user.nix
+++ b/nixos/modules/system/boot/systemd/user.nix
@@ -109,7 +109,12 @@ in {
     ];
 
     environment.etc = {
-      "systemd/user".source = generateUnits "user" cfg.units upstreamUserUnits [];
+      "systemd/user".source = generateUnits {
+        type = "user";
+        inherit (cfg) units;
+        upstreamUnits = upstreamUserUnits;
+        upstreamWants = [];
+      };
 
       "systemd/user.conf".text = ''
         [Manager]