diff --git a/pkgs/os-specific/linux/kernel/generic.nix b/pkgs/os-specific/linux/kernel/generic.nix
index 25078b7d753..4af5e80a655 100644
--- a/pkgs/os-specific/linux/kernel/generic.nix
+++ b/pkgs/os-specific/linux/kernel/generic.nix
@@ -105,7 +105,9 @@ let
       sed -e '/fflush(stdout);/i\printf("###");' -i scripts/kconfig/conf.c
     '';
 
-    inherit (kernel) src patches preUnpack;
+    preUnpack = kernel.preUnpack or "";
+
+    inherit (kernel) src patches;
 
     buildPhase = ''
       export buildRoot="''${buildRoot:-build}"
diff --git a/pkgs/os-specific/linux/kernel/manual-config.nix b/pkgs/os-specific/linux/kernel/manual-config.nix
index b2171067307..7d12af9811a 100644
--- a/pkgs/os-specific/linux/kernel/manual-config.nix
+++ b/pkgs/os-specific/linux/kernel/manual-config.nix
@@ -90,9 +90,6 @@ let
 
       inherit src;
 
-      preUnpack = ''
-      '';
-
       patches = map (p: p.patch) kernelPatches;
 
       prePatch = ''