diff --git a/cpu/at32ap/Makefile b/cpu/at32ap/Makefile
index 100cf3e..e08f273 100644
--- a/cpu/at32ap/Makefile
+++ b/cpu/at32ap/Makefile
@@ -35,6 +35,7 @@
 COBJS-y			+= cache.o
 COBJS-y			+= interrupts.o
 COBJS-$(CONFIG_PORTMUX_PIO) += portmux-pio.o
+COBJS-$(CONFIG_PORTMUX_GPIO) += portmux-gpio.o
 
 SRCS	:= $(START-y:.o=.S) $(SOBJS-y:.o=.S) $(COBJS-y:.o=.c)
 OBJS	:= $(addprefix $(obj),$(SOBJS-y) $(COBJS-y))