diff --git a/usr.sbin/i4b/isdntest/Makefile b/usr.sbin/i4b/isdntest/Makefile
index 2802f1fee236..88b491a8c8c9 100644
--- a/usr.sbin/i4b/isdntest/Makefile
+++ b/usr.sbin/i4b/isdntest/Makefile
@@ -2,6 +2,7 @@
 
 PROG=	isdntest
 MAN=	isdntest.8
+SRCS=	main.c
 
 install:
 	@${ECHO} "isdntest is not installed automatically"