diff --git a/npc/Makefile b/npc/Makefile
index 5e9d595..072bea0 100644
--- a/npc/Makefile
+++ b/npc/Makefile
@@ -28,10 +28,10 @@ NXDC_FILES := $(abspath constr/top.nxdc)
 $(SRC_AUTO_BIND): $(NXDC_FILES)
 	NVBOARD_HOME=$(NVBOARD_HOME) python3 $(NVBOARD_HOME)/scripts/auto_pin_bind.py $< $@
 
-nvboard-bin: OBJDIR := $(PREFIX)/nvobj
-nvboard-bin: SUBMAKE := $(OBJDIR)/V$(CHISEL_TOP_MODULE).mk
+nvboard-bin: OBJDIR = $(PREFIX)/nvobj
+nvboard-bin: SUBMAKE = $(OBJDIR)/V$(CHISEL_TOP_MODULE).mk
 # TODO: fix this awkward way to find nvboard.a
-nvboard-bin: CPPSRCS := $(addprefix $(PWD)/,$(wildcard csrc_nvboard/*.cpp)) $(SRC_AUTO_BIND) $(NVBOARD_HOME)/build/nvboard.a
+nvboard-bin: CPPSRCS = $(addprefix $(PWD)/,$(wildcard csrc_nvboard/*.cpp)) $(SRC_AUTO_BIND) $(NVBOARD_HOME)/build/nvboard.a
 nvboard-bin: CXXFLAGS += -I$(NVBOARD_HOME)/include $(shell sdl2-config --cflags) -g
 
 nvboard-bin: $(CPPSRCS) $(SUBMAKE) $(SRC_AUTO_BIND) $(OBJDIR)/V$(CHISEL_TOP_MODULE)