diff --git a/test/OptionalRequiredTest.cpp b/test/OptionalRequiredTest.cpp
index 5743ce3..7472603 100644
--- a/test/OptionalRequiredTest.cpp
+++ b/test/OptionalRequiredTest.cpp
@@ -15,6 +15,10 @@
  * KIND, either express or implied. See the License for the
  * specific language governing permissions and limitations
  * under the License.
+ *
+ * Contains some contributions under the Thrift Software License.
+ * Please see doc/old-thrift-license.txt in the Thrift distribution for
+ * details.
  */
 
 #include <cassert>