diff --git a/README.md b/README.md
index bbe2eae..013094c 100644
--- a/README.md
+++ b/README.md
@@ -7,6 +7,10 @@ This program is distributed in the hope that it will be useful, but WITHOUT ANY
 
 You should have received a copy of the GNU General Public License along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+## WARNING
+
+This library is experimental and should be considered subject to change at any time.
+
 ## Summary
 
 A simple C testing framework for Plan9