diff --git a/src/client.h b/src/client.h
index 35f7982..b2e714b 100644
--- a/src/client.h
+++ b/src/client.h
@@ -7,7 +7,7 @@
 
 class RPCClient {
     RpcDecoder<>* decoder = nullptr;
-    int _waiting_msg_id;
+    uint32_t _waiting_msg_id;
 
 public:
     RpcError lastError;
@@ -22,7 +22,7 @@ class RPCClient {
 
     template<typename... Args>
     void notify(const MsgPack::str_t method, Args&&... args)  {
-        int _id;
+        uint32_t _id;
         decoder->send_call(NOTIFY_MSG, method, _id, std::forward<Args>(args)...);
     }
 
@@ -46,7 +46,7 @@ class RPCClient {
 
     template<typename... Args>
     bool send_rpc(const MsgPack::str_t method, Args&&... args) {
-        int msg_id;
+        uint32_t msg_id;
         if (decoder->send_call(CALL_MSG, method, msg_id, std::forward<Args>(args)...)) {
             _waiting_msg_id = msg_id;
             return true;
diff --git a/src/decoder.h b/src/decoder.h
index 60521ec..3b91e38 100644
--- a/src/decoder.h
+++ b/src/decoder.h
@@ -19,7 +19,7 @@ class RpcDecoder {
     RpcDecoder(ITransport& transport) : _transport(transport) {}
 
     template<typename... Args>
-    bool send_call(const int call_type, const MsgPack::str_t method, int& msg_id, Args&&... args) {
+    bool send_call(const int call_type, const MsgPack::str_t method, uint32_t& msg_id, Args&&... args) {
 
         if (call_type!=CALL_MSG && call_type!=NOTIFY_MSG) return false;
 
@@ -58,7 +58,7 @@ class RpcDecoder {
 
         MsgPack::arr_size_t resp_size;
         int resp_type;
-        int resp_id;
+        uint32_t resp_id;
 
         if (!unpacker.deserialize(resp_size, resp_type, resp_id)) return false;
         if (resp_size.size() != RESPONSE_SIZE) return false;
@@ -157,7 +157,7 @@ class RpcDecoder {
     size_t _bytes_stored = 0;
     int _packet_type = NO_MSG;
     size_t _packet_size = 0;
-    int _msg_id = 0;
+    uint32_t _msg_id = 0;
 
     inline bool buffer_full() const { return _bytes_stored == BufferSize; }
 
diff --git a/src/server.h b/src/server.h
index 4ba5e62..4103141 100644
--- a/src/server.h
+++ b/src/server.h
@@ -58,7 +58,7 @@ class RPCServer {
         }
 
         int msg_type;
-        int msg_id;
+        uint32_t msg_id;
         MsgPack::str_t method;
         MsgPack::arr_size_t req_size;