diff --git a/overlay.nix b/overlay.nix
index 6578708..628a773 100644
--- a/overlay.nix
+++ b/overlay.nix
@@ -51,6 +51,9 @@ final: prev:
   });
 
   linuxPackagesCustom = prev.linuxPackagesFor (prev.linux.override {
+    # Don't use a compiler without compressed instructions, let the kernel
+    # configure the -march and -mabi arguments.
+    stdenv = prev.stdenv;
     structuredExtraConfig = with prev.lib.kernel; {
       KEXEC = yes;
       SERIAL_8250_DW = yes;
@@ -82,6 +85,8 @@ final: prev:
       PCI_HOST_GENERIC = yes;
 
       RISCV_ISA_C = no;
+      NONPORTABLE = yes;
+      EFI = no;
     };
   });
 }