diff --git a/fpga/src/main/resources/vcu118/sdboot/Makefile b/fpga/src/main/resources/vcu118/sdboot/Makefile
index e4636129..46078b69 100644
--- a/fpga/src/main/resources/vcu118/sdboot/Makefile
+++ b/fpga/src/main/resources/vcu118/sdboot/Makefile
@@ -5,12 +5,13 @@ BUILD_DIR := $(ROOT_DIR)/build
 CC=$(RISCV)/bin/riscv64-unknown-elf-gcc
 OBJCOPY=$(RISCV)/bin/riscv64-unknown-elf-objcopy
 OBJDUMP=$(RISCV)/bin/riscv64-unknown-elf-objdump
-CFLAGS=-march=rv64ima -mcmodel=medany -O2 -std=gnu11 -Wall -nostartfiles
+CFLAGS=-march=rv64ima_zicsr_zifencei -mcmodel=medany -O2 -std=gnu11 -Wall -nostartfiles
 CFLAGS+= -fno-common -g -DENTROPY=0 -mabi=lp64 -DNONSMP_HART=0
 CFLAGS+= -I $(ROOT_DIR)/include -I.
 LFLAGS=-static -nostdlib -L $(ROOT_DIR)/linker -T sdboot.elf.lds
 
-PBUS_CLK ?= 1000000 # default to 1MHz but really should be overridden
+# default to 1MHz but really should be overridden
+PBUS_CLK ?= 1000000
 
 default: elf bin dump