diff --git a/examples_x035/usbdevice/testtop.hidapi/Makefile b/examples_x035/usbdevice/testtop.hidapi/Makefile
index 021910cfc3cb45b2c94780e5b0dab6e623e459a0..a59f3cf694dc6b766180c32569e5d05130edc0ce 100644
--- a/examples_x035/usbdevice/testtop.hidapi/Makefile
+++ b/examples_x035/usbdevice/testtop.hidapi/Makefile
@@ -1,7 +1,7 @@
 all : testtop
 
 # to make CI happy.
-testtop.hidapi.elf : 
+testtop.hidapi.elf : testtop.c
 	gcc -o $@ $^ -I../../../minichlink -ludev
 
 testtop : testtop.c