diff --git a/nemu/Makefile b/nemu/Makefile
index 44eee8b..0991508 100644
--- a/nemu/Makefile
+++ b/nemu/Makefile
@@ -46,6 +46,7 @@ CFLAGS_BUILD += $(if $(CONFIG_CC_LTO),-flto,)
 CFLAGS_BUILD += $(if $(CONFIG_CC_DEBUG),-Og -ggdb3,)
 CFLAGS_BUILD += $(if $(CONFIG_CC_ASAN),-fsanitize=address,)
 CFLAGS_TRACE += -DITRACE_COND=$(if $(CONFIG_ITRACE_COND),$(call remove_quote,$(CONFIG_ITRACE_COND)),true)
+CFLAGS_TRACE += -DMTRACE_COND=$(if $(CONFIG_MTRACE_COND),$(call remove_quote,$(CONFIG_MTRACE_COND)),true)
 CFLAGS  += $(CFLAGS_BUILD) $(CFLAGS_TRACE) -D__GUEST_ISA__=$(GUEST_ISA)
 LDFLAGS += $(CFLAGS_BUILD)
 
diff --git a/nemu/scripts/build.mk b/nemu/scripts/build.mk
index ff7bae5..51350e8 100644
--- a/nemu/scripts/build.mk
+++ b/nemu/scripts/build.mk
@@ -22,8 +22,7 @@ CXX := g++
 endif
 LD := $(CXX)
 INCLUDES = $(addprefix -I, $(INC_PATH))
-DEFINE = _
-CFLAGS  := -O2 -MMD -Wall -Werror $(INCLUDES) $(CFLAGS) -D$(DEFINE)
+CFLAGS  := -O2 -MMD -Wall -Werror $(INCLUDES) $(CFLAGS)
 LDFLAGS := -O2 $(LDFLAGS)
 
 OBJS = $(SRCS:%.c=$(OBJ_DIR)/%.o) $(CXXSRC:%.cc=$(OBJ_DIR)/%.o)