diff --git a/nixos/modules/installer/cd-dvd/iso-image.nix b/nixos/modules/installer/cd-dvd/iso-image.nix
index 63abf88cab09..724421c0d910 100644
--- a/nixos/modules/installer/cd-dvd/iso-image.nix
+++ b/nixos/modules/installer/cd-dvd/iso-image.nix
@@ -335,12 +335,13 @@ let
       set textmode=true
       terminal_output console
     }
+    '' + lib.optionalString (config.isoImage.grubTheme != null) ''
     hiddenentry 'GUI mode' --hotkey 'g' {
       $(find ${config.isoImage.grubTheme} -iname '*.pf2' -printf "loadfont (\$root)/EFI/BOOT/grub-theme/%P\n")
       set textmode=false
       terminal_output gfxterm
     }
-
+    '' + ''
 
     # If the parameter iso_path is set, append the findiso parameter to the kernel
     # line. We need this to allow the nixos iso to be booted from grub directly.