diff --git a/samples/ftrace/ftrace-direct-multi.c b/samples/ftrace/ftrace-direct-multi.c
index 2a5b1fb..b6d7806 100644
--- a/samples/ftrace/ftrace-direct-multi.c
+++ b/samples/ftrace/ftrace-direct-multi.c
@@ -5,6 +5,8 @@
 #include <linux/ftrace.h>
 #include <linux/sched/stat.h>
 
+extern void my_direct_func(unsigned long ip);
+
 void my_direct_func(unsigned long ip)
 {
 	trace_printk("ip %lx\n", ip);