diff --git a/utils/src/lib.rs b/utils/src/lib.rs
index e792644..d21d6e9 100644
--- a/utils/src/lib.rs
+++ b/utils/src/lib.rs
@@ -1,5 +1,10 @@
 #![no_std]
 
+// Support for loading sel4 & co directly from the tarball. This is only
+// used when running in simulation where there is no SPI Flash support
+// (the elfloader capsule calls out to load_sel4 based on whether it
+// detects fpga hardware or not).
+
 use matcha_hal::dprintf;
 use matcha_hal::mailbox_hal::MailboxHAL;
 
@@ -18,7 +23,6 @@
         // Look in our tar file for the ELFs we need to boot Shodan.
         let sel4_elf = elf_loader::find_elf("kernel");
         let capdl_elf = elf_loader::find_elf("capdl-loader");
-        let (_, builtins_size) = tar_loader::find_file("cantrip-builtins");
 
         if sel4_elf.is_null() {
             dprintf!("Boot failure, seL4 kernel ELF missing in FLASH.\n");
@@ -30,11 +34,6 @@
             return;
         }
 
-        if builtins_size == 0 {
-            // NB: not present on Renode where the file is loaded directly.
-            dprintf!("WARNING, cantrip-builtins missing in FLASH; ignoring\r\n");
-        }
-
         // If we found all of them, boot in Shodan mode.
         dprintf!("Loading seL4 kernel elf\n");
         elf_loader::load_elf_segments(sel4_elf.as_ref().unwrap(), 0);
@@ -50,9 +49,8 @@
             ui_p_reg_start - elf_loader::elf_phys_min(capdl_segments),
         );
 
-        if builtins_size != 0 {
-            tar_loader::copy_file("cantrip-builtins", 0x50380000);
-        }
+        // NB: Renode loads the cantrip-builtins cpioarchive to the SMC memory
+        // carve-out so there's nothing to do here.
 
         dprintf!("Starting management core\n");