diff --git a/pkgs/os-specific/linux/kernel/manual-config.nix b/pkgs/os-specific/linux/kernel/manual-config.nix
index ae226f0908b..dd199814760 100644
--- a/pkgs/os-specific/linux/kernel/manual-config.nix
+++ b/pkgs/os-specific/linux/kernel/manual-config.nix
@@ -38,7 +38,7 @@ in {
 
 let
   inherit (stdenv.lib)
-    hasAttr getAttr optional optionalString maintainers platforms;
+    hasAttr getAttr optional optionalString optionalAttrs maintainers platforms;
 
   installkernel = writeTextFile { name = "installkernel"; executable=true; text = ''
     #!${stdenv.shell} -e
@@ -73,9 +73,7 @@ let
 
       installsFirmware = (config.isEnabled "FW_LOADER") &&
         (isModular || (config.isDisabled "FIRMWARE_IN_KERNEL"));
-    in {
-      outputs = if isModular then [ "out" "dev" ] else null;
-
+    in (optionalAttrs isModular { outputs = [ "out" "dev" ]; }) // {
       passthru = {
         inherit version modDirVersion config kernelPatches;
       };