diff --git a/example/echo_server.c b/example/echo_server.c
index c632768..c9cfba1 100644
--- a/example/echo_server.c
+++ b/example/echo_server.c
@@ -21,6 +21,8 @@
 #include <stdio.h>
 #include <unistd.h>
 
+int err(tailscale ts);
+
 int main(void) {
 	int ret;