diff -Nru a/chatcleaner.proto b/chatcleaner.proto
--- a/chatcleaner.proto	2017-08-16 14:24:03.000000000 +0200
+++ b/chatcleaner.proto	2018-04-15 22:27:12.245524157 +0200
@@ -29,6 +29,8 @@
  * as that of the covered work.                                              *
  *****************************************************************************/
 
+syntax = "proto2";
+
 option java_package = "de.chatcleaner.protocol";
 option java_outer_classname = "ProtoBuf";
 option optimize_for = LITE_RUNTIME;
diff -Nru a/pokerth.proto b/pokerth.proto
--- a/pokerth.proto	2017-08-16 14:24:03.000000000 +0200
+++ b/pokerth.proto	2018-04-15 22:28:04.303884308 +0200
@@ -29,6 +29,8 @@
  * as that of the covered work.                                              *
  *****************************************************************************/
 
+syntax = "proto2";
+
 option java_package = "de.pokerth.protocol";
 option java_outer_classname = "ProtoBuf";
 option optimize_for = LITE_RUNTIME;
@@ -701,7 +703,7 @@
 
 message ErrorMessage {
 	enum ErrorReason {
-		reserved = 0;
+		custReserved = 0;
 		initVersionNotSupported = 1;
 		initServerFull = 2;
 		initAuthFailure = 3;
diff -Nru a/src/net/common/netpacket.cpp b/src/net/common/netpacket.cpp
--- a/src/net/common/netpacket.cpp	2017-08-16 14:24:03.000000000 +0200
+++ b/src/net/common/netpacket.cpp	2018-04-15 22:28:44.660128335 +0200
@@ -249,7 +249,7 @@
 		retVal = ErrorMessage::sessionTimeout;
 		break;
 	default :
-		retVal = ErrorMessage::reserved;
+		retVal = ErrorMessage::custReserved;
 		break;
 	}
 	return retVal;