diff --git a/Makefile b/Makefile
index b81ffcb..47bdee5 100644
--- a/Makefile
+++ b/Makefile
@@ -157,6 +157,8 @@
 	@echo '   test-list            - lists all test targets'
 	@echo ''
 	@echo 'Test Parameters:'
+	@echo '   CROSVM_TAR_GZ        - path to a custom cvd-host_package.tar.gz'
+	@echo '                          (default: uses a pre-built version)'
 	@echo '   VM_IMAGE             - path to an image to be used by the VMM to boot the VM'
 	@echo '                          (default: uses the host image)'
 	@echo ''
@@ -313,8 +315,12 @@
 PREBUILTS_QEMU_ROM := prebuilts/linux-aarch64/images/efi-virtio.rom
 PREBUILTS_QEMU_BIN := prebuilts/linux-x86/qemu
 
+ifeq ($(CROSVM_TAR_GZ),)
 CROSVM_TAR_GZ := $(PREBUILTS_CROSVM_TAR_GZ)
+CROSVM_EXT4 := $(OUT_DIR)/images/prebuilt-crosvm.ext4
+else
 CROSVM_EXT4 := $(OUT_DIR)/images/crosvm.ext4
+endif
 
 .PHONY:update-prebuilts
 update-prebuilts: \