diff --git a/example-cdc/Makefile b/example-cdc/Makefile
index 4eebd81..1d64f78 100644
--- a/example-cdc/Makefile
+++ b/example-cdc/Makefile
@@ -10,6 +10,7 @@ CHIP=stm32f103
 
 USE_SYS = yes
 USE_USB = yes
+ENABLE_OUTPUT_HEX=yes
 
 ###################################
 CROSS = arm-none-eabi-
@@ -19,7 +20,7 @@ OBJCOPY   = $(CROSS)objcopy
 
 MCU   = cortex-m3
 CWARN = -Wall -Wextra -Wstrict-prototypes
-DEFS  = -DUSE_SYS3 -DFREE_STANDING
+DEFS  = -DUSE_SYS3 -DFREE_STANDING -DMHZ=72
 OPT   = -O3 -Os -g
 LIBS  =
 
diff --git a/example-usb-serial/Makefile b/example-usb-serial/Makefile
index 99d4f8f..168b913 100644
--- a/example-usb-serial/Makefile
+++ b/example-usb-serial/Makefile
@@ -20,7 +20,7 @@ OBJCOPY   = $(CROSS)objcopy
 
 MCU   = cortex-m3
 CWARN = -Wall -Wextra -Wstrict-prototypes
-DEFS  = -DUSE_SYS3 -DFREE_STANDING
+DEFS  = -DUSE_SYS3 -DFREE_STANDING -DMHZ=72
 OPT   = -O3 -Os -g
 LIBS  =