diff --git a/pc-bios/optionrom/Makefile b/pc-bios/optionrom/Makefile
index 51da288..2caf7e6 100644
--- a/pc-bios/optionrom/Makefile
+++ b/pc-bios/optionrom/Makefile
@@ -16,6 +16,9 @@
 
 build-all: multiboot.bin linuxboot.bin
 
+# suppress auto-removal of intermediate files
+.SECONDARY:
+
 %.img: %.o
 	$(call quiet-command,$(LD) -Ttext 0 -e _start -s -o $@ $<,"  Building $(TARGET_DIR)$@")