diff --git a/src/Makefile b/src/Makefile
index e8f1a40..a673939 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -32,7 +32,7 @@ include $(HOST)/Makefile.inc
 OBJ = $(SRC:.c=.o)
 
 blackmagic: $(OBJ)
-	$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)
+	$(CC) -o $@ $^ $(LDFLAGS)
 
 .PHONY:	clean host_clean
 
diff --git a/src/stm32/Makefile.inc b/src/stm32/Makefile.inc
index 20a1329..e498a3b 100644
--- a/src/stm32/Makefile.inc
+++ b/src/stm32/Makefile.inc
@@ -2,10 +2,11 @@ CROSS_COMPILE ?= arm-cortexm3-eabi-
 CC = $(CROSS_COMPILE)gcc
 OBJCOPY = $(CROSS_COMPILE)objcopy
 
-CFLAGS += -Istm32/include
+CFLAGS += -Istm32/include -mcpu=cortex-m3 -mthumb -msoft-float
 LDFLAGS_BOOT = -lopencm3_stm32 -Wl,--defsym,_stack=0x20005000 \
-	-Wl,-T,stm32/blackmagic.ld -nostartfiles -lc -lnosys -Wl,-Map=mapfile
-LDFLAGS = $(LDFLAGS_BOOT) -Wl,-Ttext=0x8002000
+	-Wl,-T,stm32/blackmagic.ld -nostartfiles -lc -lnosys -Wl,-Map=mapfile \
+	-mthumb -march=armv7 -mfix-cortex-m3-ldrd -msoft-float
+LDFLAGS = $(LDFLAGS_BOOT) -Wl,-Ttext=0x8002000 -mthumb -march=armv7 -mfix-cortex-m3-ldrd -msoft-float
 
 SRC += 	cdcacm.c	\
 	platform.c	\
@@ -15,8 +16,8 @@ all:	blackmagic.bin blackmagic_dfu.bin
 blackmagic.bin:	blackmagic
 	$(OBJCOPY) -O binary $^ $@
 
-blackmagic_dfu: usbdfu.c
-	$(CC) $(CFLAGS) $^ -o $@ $(LDFLAGS_BOOT)
+blackmagic_dfu: usbdfu.o
+	$(CC) $^ -o $@ $(LDFLAGS_BOOT)
 
 blackmagic_dfu.bin:	blackmagic_dfu
 	$(OBJCOPY) -O binary $^ $@