diff --git a/compiler/cpp/Makefile.am b/compiler/cpp/Makefile.am
index 3838fac..fa8d1ca 100644
--- a/compiler/cpp/Makefile.am
+++ b/compiler/cpp/Makefile.am
@@ -16,6 +16,10 @@
 # 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.
 
 AM_YFLAGS = -d
 BUILT_SOURCES =