diff --git a/lib/latency-format.proto b/lib/latency-format.proto
index 908e822f6a68c803aed84b7c95a02e4ddb16b8ee..d8d5e97bd857a645b89b3c4c9b2529a3c23944f6 100644
--- a/lib/latency-format.proto
+++ b/lib/latency-format.proto
@@ -1,3 +1,5 @@
+syntax = "proto2";
+
 package transport.latency.format;
 
 message LatencyDist
diff --git a/lib/tests/simtransport-testmessage.proto b/lib/tests/simtransport-testmessage.proto
index 0b0dddebdcc099ed4e24c626682d67cab6436cc1..66dfa05c58c4dc3cd9ad34021178520d534046c5 100644
--- a/lib/tests/simtransport-testmessage.proto
+++ b/lib/tests/simtransport-testmessage.proto
@@ -1,3 +1,5 @@
+syntax = "proto2";
+
 package transport.test;
 
 message TestMessage {
diff --git a/lockserver/locks-proto.proto b/lockserver/locks-proto.proto
index 59840a3ac451757a648dd7b159f793efcfcbfb72..b8764979c54f555739cc93a3e412990c70e6e4e4 100644
--- a/lockserver/locks-proto.proto
+++ b/lockserver/locks-proto.proto
@@ -1,3 +1,5 @@
+syntax = "proto2";
+
 package lockserver.proto;
 
 message Request {
diff --git a/replication/common/request.proto b/replication/common/request.proto
index 9a76ec1d47837a55d43bd99a1896e4d46aacab21..70de3d94dbded79dc110206b226dd2b9048e297d 100644
--- a/replication/common/request.proto
+++ b/replication/common/request.proto
@@ -1,3 +1,5 @@
+syntax = "proto2";
+
 package replication;
 
 message Request {
diff --git a/replication/ir/ir-proto.proto b/replication/ir/ir-proto.proto
index 500d21922be36884efaf654348e70b277f07c8b7..3880a39b87e800b1bd78492dcce5408dd3f966dc 100644
--- a/replication/ir/ir-proto.proto
+++ b/replication/ir/ir-proto.proto
@@ -1,3 +1,5 @@
+syntax = "proto2";
+
 import "replication/common/request.proto";
 
 package replication.ir.proto;
diff --git a/replication/vr/vr-proto.proto b/replication/vr/vr-proto.proto
index 7177a4a9c778c408c47ac9576d961a14aebaca91..902f04159cbc33ad4476184deb6c840e91b98d47 100644
--- a/replication/vr/vr-proto.proto
+++ b/replication/vr/vr-proto.proto
@@ -1,3 +1,5 @@
+syntax = "proto2";
+
 import "replication/common/request.proto";
 
 package replication.vr.proto;
diff --git a/store/common/common-proto.proto b/store/common/common-proto.proto
index 71587321d229d235e8ae62962eb1500aae8bcba8..362fc93d6612a299fb66483696e51f49cd2ae118 100644
--- a/store/common/common-proto.proto
+++ b/store/common/common-proto.proto
@@ -1,3 +1,5 @@
+syntax = "proto2";
+
 message TimestampMessage {
     required uint64 id = 1;
     required uint64 timestamp = 2;
diff --git a/store/strongstore/strong-proto.proto b/store/strongstore/strong-proto.proto
index f6bb557d5127b566a385969b28ff7c4988495cf8..5ff4f7c40b760566a2c6be3cc971ad17840e9628 100644
--- a/store/strongstore/strong-proto.proto
+++ b/store/strongstore/strong-proto.proto
@@ -1,3 +1,5 @@
+syntax = "proto2";
+
 import "store/common/common-proto.proto";
 
 package strongstore.proto;
diff --git a/store/tapirstore/tapir-proto.proto b/store/tapirstore/tapir-proto.proto
index 1b2913adbb80282f89530cc12660ff3f0a993c2b..a7a0dfa07fd7be916b72804c21d963bc75cac1af 100644
--- a/store/tapirstore/tapir-proto.proto
+++ b/store/tapirstore/tapir-proto.proto
@@ -1,3 +1,5 @@
+syntax = "proto2";
+
 import "store/common/common-proto.proto";
 
 package tapirstore.proto;
diff --git a/store/weakstore/weak-proto.proto b/store/weakstore/weak-proto.proto
index 0bab51c566e65dee7d672782ab09dd5633839e75..899f9b131ca09f997289c7c507ba7aa88e733b68 100644
--- a/store/weakstore/weak-proto.proto
+++ b/store/weakstore/weak-proto.proto
@@ -1,3 +1,5 @@
+syntax = "proto2";
+
 package weakstore.proto;
 
 message ReplyMessage {
@@ -27,4 +29,4 @@ message PutMessage {
 
 message PutReplyMessage {
     required int32 status = 1;
-}
\ No newline at end of file
+}
diff --git a/test-client/test-client-proto.proto b/test-client/test-client-proto.proto
index b928f07479700054a5bfb68e3dfc8304813d8cc1..1895637398031dbd07f12291bc59d04ef072b3d3 100644
--- a/test-client/test-client-proto.proto
+++ b/test-client/test-client-proto.proto
@@ -1,3 +1,5 @@
+syntax = "proto2";
+
 message TestMessage {
     required int32 status = 1;
 }