diff --git a/Makefile b/Makefile
index 6ba1d6d..b50dca0 100644
--- a/Makefile
+++ b/Makefile
@@ -61,7 +61,7 @@ endif
 
 # riscv64-unknown-elf- or riscv64-linux-gnu-
 # perhaps in /opt/riscv/bin
-#TOOLPREFIX = 
+TOOLPREFIX = /opt/riscv/bin/riscv64-unknown-elf-
 
 # Try to infer the correct TOOLPREFIX if not set
 ifndef TOOLPREFIX
diff --git a/fs.img.bk b/fs.img.bk
new file mode 100644
index 0000000..b97eba1
Binary files /dev/null and b/fs.img.bk differ