diff --git a/benchmark/addressbook.proto b/benchmark/addressbook.proto
index fc79075..1c08c6b 100644
--- a/benchmark/addressbook.proto
+++ b/benchmark/addressbook.proto
@@ -1,8 +1,11 @@
+syntax = "proto2";
+
 package tutorial;
 
 message Person {
   required string name = 1;
   required int32 id = 2;
+  required string email = 3;
 
   enum PhoneType {
     MOBILE = 0;
@@ -15,7 +18,7 @@ message Person {
     optional PhoneType type = 2 [default = HOME];
   }
 
-  repeated PhoneNumber phone = 3;
+  repeated PhoneNumber phone = 4;
 }
 
 message AddressBook {
diff --git a/benchmark/carsales.proto b/benchmark/carsales.proto
index 5ec587e..0b6a975 100644
--- a/benchmark/carsales.proto
+++ b/benchmark/carsales.proto
@@ -21,6 +21,8 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+syntax = "proto2";
+
 package capnp.benchmark.protobuf;
 
 message ParkingLot {
diff --git a/benchmark/catrank.proto b/benchmark/catrank.proto
index 87f2cf8..c3f55ae 100644
--- a/benchmark/catrank.proto
+++ b/benchmark/catrank.proto
@@ -21,6 +21,8 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+syntax = "proto2";
+
 package capnp.benchmark.protobuf;
 
 message SearchResultList {
diff --git a/benchmark/eval.proto b/benchmark/eval.proto
index 4c6f72c..204a081 100644
--- a/benchmark/eval.proto
+++ b/benchmark/eval.proto
@@ -21,6 +21,8 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+syntax = "proto2";
+
 package capnp.benchmark.protobuf;
 
 enum Operation {