more explicit test spec
diff --git a/configure.ac b/configure.ac
index cb014d1..64810bb 100644
--- a/configure.ac
+++ b/configure.ac
@@ -132,6 +132,7 @@
 skeletons/Makefile			\
 examples/Makefile			\
 doc/man/Makefile			\
+tests/Makefile				\
 asn1c/Makefile				\
 doc/Makefile				\
 Makefile				\