diff --git a/include/modbuspp/asciilayer.h b/include/modbuspp/asciilayer.h
index c0393c1..c5094d8 100644
--- a/include/modbuspp/asciilayer.h
+++ b/include/modbuspp/asciilayer.h
@@ -46,6 +46,11 @@ namespace Modbus {
        */
       AsciiLayer (const std::string & port, const std::string & settings);
 
+      /**
+      * @brief Destructor
+      */
+      virtual ~AsciiLayer() = default;
+
       /**
        * @brief Name of the serial port
        *
diff --git a/src/asciilayer_p.h b/src/asciilayer_p.h
index d406252..aa73813 100644
--- a/src/asciilayer_p.h
+++ b/src/asciilayer_p.h
@@ -25,6 +25,7 @@ namespace Modbus {
 
     public:
       Private (const std::string & port, const std::string & settings);
+      virtual ~Private() = default;
 
       int oneByteTime;
   };
diff --git a/src/device_p.h b/src/device_p.h
index 1685b3c..bf58f86 100644
--- a/src/device_p.h
+++ b/src/device_p.h
@@ -28,6 +28,7 @@ namespace Modbus {
 
     public:
       Private (Device * q);
+      virtual ~Private() = default;
       virtual void setBackend (Net net, const std::string & connection,
                                const std::string & settings);
       virtual void setConfig (const nlohmann::json & config);
diff --git a/src/master_p.h b/src/master_p.h
index 6b3ba2e..c6aa5d5 100644
--- a/src/master_p.h
+++ b/src/master_p.h
@@ -26,6 +26,7 @@ namespace Modbus {
 
     public:
       Private (Master * q);
+      virtual ~Private() = default;
 
       void setBackend (Net net, const std::string & connection,
                                const std::string & settings) override;
@@ -39,4 +40,3 @@ namespace Modbus {
 }
 
 /* ========================================================================== */
-
diff --git a/src/netlayer_p.h b/src/netlayer_p.h
index a8a87d9..d39cf9a 100644
--- a/src/netlayer_p.h
+++ b/src/netlayer_p.h
@@ -24,6 +24,7 @@ namespace Modbus {
     public:
       Private (Net n, const std::string & c, const std::string & s, uint16_t m) :
         net (n), connection (c), settings (s), maxAduLength (m)  {}
+      virtual ~Private() = default;
 
       Net net;
       std::string connection;
diff --git a/src/router_p.h b/src/router_p.h
index 31197a2..3f8eccc 100644
--- a/src/router_p.h
+++ b/src/router_p.h
@@ -25,6 +25,7 @@ namespace Modbus {
 
     public:
       Private (Router * q);
+      virtual ~Private() = default;
       virtual void setConfig (const nlohmann::json & config);
 
       virtual bool open();
diff --git a/src/rtulayer_p.h b/src/rtulayer_p.h
index f80bb9d..ea3d754 100644
--- a/src/rtulayer_p.h
+++ b/src/rtulayer_p.h
@@ -25,6 +25,7 @@ namespace Modbus {
 
     public:
       Private (const std::string & port, const std::string & settings);
+      virtual ~Private() = default;
 
       int oneByteTime;
   };
diff --git a/src/server.cpp b/src/server.cpp
index 853ab26..840fa42 100644
--- a/src/server.cpp
+++ b/src/server.cpp
@@ -496,7 +496,7 @@ namespace Modbus {
 
   // ---------------------------------------------------------------------------
   // static
-  void * Server::Private::loop (std::future<void> run, Private * d) {
+  void Server::Private::loop (std::future<void> run, Private * d) {
     int rc;
 
     while (run.wait_for (std::chrono::milliseconds (100)) == std::future_status::timeout) {
diff --git a/src/server_p.h b/src/server_p.h
index e1fe1c7..0fcc824 100644
--- a/src/server_p.h
+++ b/src/server_p.h
@@ -30,6 +30,7 @@ namespace Modbus {
       static const int MAX_CONNECTIONS = 16;
     public:
       Private (Server * q);
+      virtual ~Private() = default;
       virtual void setBackend (Net net, const std::string & connection,
                                const std::string & settings);
       virtual void setConfig (const nlohmann::json & config);
@@ -41,7 +42,7 @@ namespace Modbus {
 
       BufferedSlave * addSlave (int slaveAddr, Device * master);
 
-      static void * loop (std::future<void> run, Private * d);
+      static void loop (std::future<void> run, Private * d);
       static int receive (Private * d);
 
       int listen_sock = -1;
diff --git a/src/slave_p.h b/src/slave_p.h
index 736f303..b3c8700 100644
--- a/src/slave_p.h
+++ b/src/slave_p.h
@@ -28,6 +28,7 @@ namespace Modbus {
     public:
       Private (Slave * q);
       Private (Slave * q, int s, Device * d);
+      virtual ~Private() = default;
 
       inline modbus_t * ctx() {
         return dev->backend().context();
diff --git a/src/tcplayer_p.h b/src/tcplayer_p.h
index 0aa28fe..a3fb590 100644
--- a/src/tcplayer_p.h
+++ b/src/tcplayer_p.h
@@ -25,6 +25,7 @@ namespace Modbus {
 
     public:
       Private (const std::string & host, const std::string & service);
+      virtual ~Private() = default;
 
       uint16_t transactionId;
   };