diff --git a/src/olink/clientnode.cpp b/src/olink/clientnode.cpp
index 4c99a83..70fcbed 100644
--- a/src/olink/clientnode.cpp
+++ b/src/olink/clientnode.cpp
@@ -9,7 +9,6 @@ namespace ApiGear { namespace ObjectLink {
 ClientNode::ClientNode(ClientRegistry& registry)
     : BaseNode()
     , m_registry(registry)
-    , m_nextRequestId(0)
 {
 }
 
@@ -49,8 +48,8 @@ void ClientNode::invokeRemote(const std::string& methodId, const nlohmann::json&
 {
     static const std::string invokeRemoteLog = "ClientNode.invokeRemote: ";
     emitLog(LogLevel::Info, invokeRemoteLog, methodId);
-    int requestId = nextRequestId();
     std::unique_lock<std::mutex> lock(m_pendingInvokesMutex);
+    auto requestId = nextRequestId();
     m_invokesPending[requestId] = func;
     lock.unlock();
     nlohmann::json msg = Protocol::invokeMessage(requestId, methodId, args);
@@ -113,7 +112,7 @@ void ClientNode::handlePropertyChange(const std::string& propertyId, const nlohm
     }
 }
 
-void ClientNode::handleInvokeReply(int requestId, const std::string& methodId, const nlohmann::json& value)
+void ClientNode::handleInvokeReply(unsigned int requestId, const std::string& methodId, const nlohmann::json& value)
 {
     static const std::string handleInvokeLog = "ClientNode.handleInvokeReply: ";
     emitLogWithPayload(LogLevel::Info, value, handleInvokeLog, methodId);
@@ -154,12 +153,9 @@ void ClientNode::handleError(int msgType, int requestId, const std::string& erro
     emitLog(LogLevel::Info, errorLog, std::to_string(msgType), std::to_string(requestId), error);
 }
 
-int ClientNode::nextRequestId()
+unsigned int ClientNode::nextRequestId()
 {
     m_nextRequestId++;
-    if (m_nextRequestId < 0){
-        m_nextRequestId = 0;
-    }
     return m_nextRequestId;
 }
 
diff --git a/src/olink/clientnode.h b/src/olink/clientnode.h
index e4514f8..cf1e713 100644
--- a/src/olink/clientnode.h
+++ b/src/olink/clientnode.h
@@ -74,7 +74,7 @@ class OLINK_EXPORT ClientNode : public BaseNode, public IClientNode, public std:
     /** IProtocolListener::handlePropertyChange implementation */
     void handlePropertyChange(const std::string& propertyId, const nlohmann::json& value) override;
     /** IProtocolListener::handleInvokeReply implementation */
-    void handleInvokeReply(int requestId, const std::string& methodId, const nlohmann::json& value) override;
+    void handleInvokeReply(unsigned int requestId, const std::string& methodId, const nlohmann::json& value) override;
     /** IProtocolListener::handleSignal implementation */
     void handleSignal(const std::string& signalId, const nlohmann::json& args) override;
     /** IProtocolListener::handleError implementation */
@@ -84,7 +84,7 @@ class OLINK_EXPORT ClientNode : public BaseNode, public IClientNode, public std:
      * Returns a request id for outgoing messages.
      * @return a unique, non negative id.
      */
-    int nextRequestId();
+    unsigned int nextRequestId();
 private:
     /* The registry in which client is registered and which provides sinks connected with this node*/
     ClientRegistry& m_registry;
@@ -92,9 +92,9 @@ class OLINK_EXPORT ClientNode : public BaseNode, public IClientNode, public std:
     unsigned long m_nodeId;
 
     /* Value of last request id.*/
-    std::atomic<int> m_nextRequestId;
+    std::atomic<unsigned int> m_nextRequestId = {0};
     /** Collection of callbacks for method replies that client is waiting for associated with the id for invocation request message.*/
-    std::map<int,InvokeReplyFunc> m_invokesPending;
+    std::map<unsigned int,InvokeReplyFunc> m_invokesPending;
     std::mutex m_pendingInvokesMutex;
 };
 
diff --git a/src/olink/core/basenode.cpp b/src/olink/core/basenode.cpp
index 28d3965..a94074e 100644
--- a/src/olink/core/basenode.cpp
+++ b/src/olink/core/basenode.cpp
@@ -44,7 +44,7 @@ void BaseNode::handleUnlink(const std::string& objectId)
     emitLog(LogLevel::Warning, notImplementedLog, std::string(__func__), objectId);
 }
 
-void BaseNode::handleInvoke(int, const std::string& methodId, const nlohmann::json& args)
+void BaseNode::handleInvoke(unsigned int, const std::string& methodId, const nlohmann::json& args)
 {
     emitLogWithPayload(LogLevel::Warning, args, notImplementedLog, std::string(__func__), methodId, " args ");
 }
@@ -59,7 +59,7 @@ void BaseNode::handleInit(const std::string& objectId, const nlohmann::json& pro
     emitLogWithPayload(LogLevel::Warning, props, notImplementedLog, std::string(__func__), objectId, " props ");
 }
 
-void BaseNode::handleInvokeReply(int requestId, const std::string& methodId, const nlohmann::json& value)
+void BaseNode::handleInvokeReply(unsigned int requestId, const std::string& methodId, const nlohmann::json& value)
 {
     emitLog(LogLevel::Warning, notImplementedLog, std::string(__func__), methodId, " requestId ", std::to_string(requestId), " value ", value);
 }
diff --git a/src/olink/core/basenode.h b/src/olink/core/basenode.h
index c92aeef..36ebfc4 100644
--- a/src/olink/core/basenode.h
+++ b/src/olink/core/basenode.h
@@ -42,13 +42,13 @@ class OLINK_EXPORT BaseNode: public LoggerBase,
     // Empty, logging only implementation of IProtocolListener::handleUnlink, should be overwritten on server side.
     void handleUnlink(const std::string& objectId) override;
     // Empty, logging only implementation of IProtocolListener::handleInvoke, should be overwritten on server side.
-    void handleInvoke(int requestId, const std::string& methodId, const nlohmann::json& args) override;
+    void handleInvoke(unsigned int requestId, const std::string& methodId, const nlohmann::json& args) override;
     // Empty, logging only implementation of IProtocolListener::handleSetProperty, should be overwritten on server side.
     void handleSetProperty(const std::string& propertyId, const nlohmann::json& value) override;
     // Empty, logging only implementation of IProtocolListener::handleInit, should be overwritten on client side.
     void handleInit(const std::string& objectId, const nlohmann::json& props) override;
     // Empty, logging only implementation of IProtocolListener::handleInvokeReply, should be overwritten on client side.
-    void handleInvokeReply(int requestId, const std::string& methodId, const nlohmann::json& value) override;
+    void handleInvokeReply(unsigned int requestId, const std::string& methodId, const nlohmann::json& value) override;
     // Empty, logging only implementation of IProtocolListener::handleSignal, should be overwritten on client side.
     void handleSignal(const std::string& signalId, const nlohmann::json& args) override;
     // Empty, logging only implementation of IProtocolListener::handlePropertyChange, should be overwritten on client side.
diff --git a/src/olink/core/protocol.cpp b/src/olink/core/protocol.cpp
index 6b8082e..fff43c8 100644
--- a/src/olink/core/protocol.cpp
+++ b/src/olink/core/protocol.cpp
@@ -65,14 +65,14 @@ nlohmann::json Protocol::propertyChangeMessage(const std::string& propertyId, co
                 );
 }
 
-nlohmann::json Protocol::invokeMessage(int requestId, const std::string& methodId, const nlohmann::json& args)
+nlohmann::json Protocol::invokeMessage(unsigned int requestId, const std::string& methodId, const nlohmann::json& args)
 {
     return nlohmann::json::array(
                 { MsgType::Invoke, requestId, methodId, args }
                 );
 }
 
-nlohmann::json Protocol::invokeReplyMessage(int requestId, const std::string& methodId, const nlohmann::json& value)
+nlohmann::json Protocol::invokeReplyMessage(unsigned int requestId, const std::string& methodId, const nlohmann::json& value)
 {
     return nlohmann::json::array(
                 { MsgType::InvokeReply, requestId, methodId, value }
@@ -131,14 +131,14 @@ bool Protocol::handleMessage(const nlohmann::json& msg, IProtocolListener& liste
         break;
     }
     case int(MsgType::Invoke): {
-        const auto& id = msg[1].get<int>();
+        const auto& id = msg[1].get<unsigned int>();
         const auto& methodId = msg[2].get<std::string>();
         const auto& args = msg[3].get<nlohmann::json>();
         listener.handleInvoke(id, methodId, args);
         break;
     }
     case int(MsgType::InvokeReply): {
-        const auto& id = msg[1].get<int>();
+        const auto& id = msg[1].get<unsigned int>();
         const auto& methodId = msg[2].get<std::string>();
         const auto& value = msg[3].get<nlohmann::json>();
         listener.handleInvokeReply(id, methodId, value);
diff --git a/src/olink/core/protocol.h b/src/olink/core/protocol.h
index e790937..00b578f 100644
--- a/src/olink/core/protocol.h
+++ b/src/olink/core/protocol.h
@@ -79,7 +79,7 @@ class OLINK_EXPORT IProtocolListener
      * @param methodId Unambiguously describes method in object for which invoke message was received.
      * @param args Arguments with which method should be invoked.
      */
-    virtual void handleInvoke(int requestId, const std::string& methodId, const nlohmann::json& args) = 0;
+    virtual void handleInvoke(unsigned int requestId, const std::string& methodId, const nlohmann::json& args) = 0;
     /**
      * Client side handler, handles invokeReply message.
      * @param requestId Identifier of a request with which the client requested method invocation.
@@ -87,7 +87,7 @@ class OLINK_EXPORT IProtocolListener
      * @param methodId Unambiguously describes method in object for which invokeReply message was received.
      * @param value Method's result value.
      */
-    virtual void handleInvokeReply(int requestId, const std::string& methodId, const nlohmann::json& value) = 0;
+    virtual void handleInvokeReply(unsigned int requestId, const std::string& methodId, const nlohmann::json& value) = 0;
     /**
      * Client side handler, handles signal message.
      * @param signalId Unambiguously describes signal in object for which signal message was received.
@@ -165,7 +165,7 @@ class OLINK_EXPORT Protocol : public LoggerBase
     * @param args Arguments with which method should be invoked.
     * @return Composed invokeMessage in json format.
     */
-    static nlohmann::json invokeMessage(int requestId, const std::string& methodId, const nlohmann::json& args);
+    static nlohmann::json invokeMessage(unsigned int requestId, const std::string& methodId, const nlohmann::json& args);
     /**
     * Method message.
     * Composes a response to a method invocation message for a methodId.
@@ -175,7 +175,7 @@ class OLINK_EXPORT Protocol : public LoggerBase
     * @param value Value that is an outcome of method invocation.
     * @return Composed invokeReplyMessage in json format.
     */
-    static nlohmann::json invokeReplyMessage(int requestId, const std::string& methodId, const nlohmann::json& value);
+    static nlohmann::json invokeReplyMessage(unsigned int requestId, const std::string& methodId, const nlohmann::json& value);
     /**
     * Signal message.
     * Composes a notification message for signal emitted for signalId.
diff --git a/src/olink/remotenode.cpp b/src/olink/remotenode.cpp
index 828778d..fd15a14 100644
--- a/src/olink/remotenode.cpp
+++ b/src/olink/remotenode.cpp
@@ -85,7 +85,7 @@ void RemoteNode::handleSetProperty(const std::string& propertyId, const nlohmann
     }
 }
 
-void RemoteNode::handleInvoke(int requestId, const std::string& methodId, const nlohmann::json& args)
+void RemoteNode::handleInvoke(unsigned int requestId, const std::string& methodId, const nlohmann::json& args)
 {
     auto objectId = ApiGear::ObjectLink::Name::getObjectId(methodId);
     auto source = m_registry.getSource(objectId).lock();
diff --git a/src/olink/remotenode.h b/src/olink/remotenode.h
index 6ffe6f6..4f2907c 100644
--- a/src/olink/remotenode.h
+++ b/src/olink/remotenode.h
@@ -81,7 +81,7 @@ class OLINK_EXPORT RemoteNode: public BaseNode, public IRemoteNode, public std::
     /** IProtocolListener::handleSetProperty implementation. */
     void handleSetProperty(const std::string& propertyId, const nlohmann::json& value) override;
     /** IProtocolListener::handleInvoke implementation. */
-    void handleInvoke(int requestId, const std::string& methodId, const nlohmann::json& args) override;
+    void handleInvoke(unsigned int requestId, const std::string& methodId, const nlohmann::json& args) override;
 
     /** IRemoteNode::notifyPropertyChange implementation. */
     void notifyPropertyChange(const std::string& propertyId, const nlohmann::json& value) override;
diff --git a/tests/test_protocol.cpp b/tests/test_protocol.cpp
index 2cd1528..4ebfc15 100644
--- a/tests/test_protocol.cpp
+++ b/tests/test_protocol.cpp
@@ -16,7 +16,7 @@ TEST_CASE("protocol")
     json props = {{ "count", 0 }};
     int value = 1;
     json args = {1, 2};
-    int requestId = 1;
+    unsigned int requestId = 1;
     MsgType msgType = MsgType::Invoke;
     std::string error = "failed";