diff --git a/sw/Makefile b/sw/Makefile
index 9ff58a6..c97dba5 100644
--- a/sw/Makefile
+++ b/sw/Makefile
@@ -1,4 +1,4 @@
-TOOLCHAIN_PREFIX=riscv64-unknown-elf-
+TOOLCHAIN_PREFIX?=riscv64-unknown-elf-
 
 %.elf: %.S link.ld
 	$(TOOLCHAIN_PREFIX)gcc -nostartfiles -nostdlib -march=rv32i -mabi=ilp32 -Tlink.ld -o$@ $<