tests: Fix the make distcheck of libosmocore with the tests
diff --git a/tests/ussd/Makefile.am b/tests/ussd/Makefile.am
index ef9aa49..de9ff89 100644
--- a/tests/ussd/Makefile.am
+++ b/tests/ussd/Makefile.am
@@ -1,5 +1,6 @@
 INCLUDES = $(all_includes) -I$(top_srcdir)/include
 noinst_PROGRAMS = ussd_test
+EXTRA_DIST = ussd_test.ok
 
 ussd_test_SOURCES = ussd_test.c
 ussd_test_LDADD = $(top_builddir)/src/libosmocore.la $(top_builddir)/src/gsm/libosmogsm.la