diff --git a/csharp/generate_protos.sh b/csharp/generate_protos.sh
index e6687c3..0508584 100755
--- a/csharp/generate_protos.sh
+++ b/csharp/generate_protos.sh
@@ -63,7 +63,8 @@
     csharp/protos/unittest_issue6936_c.proto \
     src/google/protobuf/unittest_well_known_types.proto \
     src/google/protobuf/test_messages_proto3.proto \
-    src/google/protobuf/test_messages_proto2.proto
+    src/google/protobuf/test_messages_proto2.proto \
+    src/google/protobuf/unittest_proto3_optional.proto
 
 # AddressBook sample protos
 $PROTOC -Iexamples -Isrc --csharp_out=csharp/src/AddressBook \