diff --git a/examples/rules.mk b/examples/rules.mk
index 4bad747da..4af2f2be4 100644
--- a/examples/rules.mk
+++ b/examples/rules.mk
@@ -170,7 +170,7 @@ flash-stlink: $(BUILD)/$(PROJECT).elf
 
 # flash with pyocd
 flash-pyocd: $(BUILD)/$(PROJECT).hex
-	pyocd flash -t $(PYOCD_TARGET) -O dap_protocol=swd $<
+	pyocd flash -t $(PYOCD_TARGET) $(PYOCD_OPTION) $<
 	pyocd reset -t $(PYOCD_TARGET)
 
 # flash with Black Magic Probe
diff --git a/hw/bsp/samd21/boards/curiosity_nano/board.mk b/hw/bsp/samd21/boards/curiosity_nano/board.mk
index 05257e88c..767788b86 100644
--- a/hw/bsp/samd21/boards/curiosity_nano/board.mk
+++ b/hw/bsp/samd21/boards/curiosity_nano/board.mk
@@ -10,4 +10,5 @@ JLINK_DEVICE = atsamd21g17a
 #flash: flash-jlink
 
 PYOCD_TARGET = atsamd21g17a
+PYOCD_OPTION = -O dap_protocol=swd
 flash: flash-pyocd