diff --git a/common/network/Socket.h b/common/network/Socket.h
index 53f957e..874a59c 100644
--- a/common/network/Socket.h
+++ b/common/network/Socket.h
@@ -82,6 +82,7 @@
   class ConnectionFilter {
   public:
     virtual bool verifyConnection(Socket* s) = 0;
+    virtual ~ConnectionFilter() {}
   };
 
   class SocketListener {
diff --git a/common/rdr/FdInStream.h b/common/rdr/FdInStream.h
index 5d9598c..b4c8765 100644
--- a/common/rdr/FdInStream.h
+++ b/common/rdr/FdInStream.h
@@ -30,6 +30,7 @@
   class FdInStreamBlockCallback {
   public:
     virtual void blockCallback() = 0;
+    virtual ~FdInStreamBlockCallback() {}
   };
 
   class FdInStream : public InStream {
diff --git a/common/rfb/SSecurityPlain.h b/common/rfb/SSecurityPlain.h
index 2c08c24..4bf42b7 100644
--- a/common/rfb/SSecurityPlain.h
+++ b/common/rfb/SSecurityPlain.h
@@ -38,6 +38,8 @@
       { return validUser(username) ? validateInternal(sc, username, password) : false; }
     static StringParameter plainUsers;
 
+    virtual ~PasswordValidator() { }
+
   protected:
     virtual bool validateInternal(SConnection* sc, const char *username, const char *password)=0;
     static bool validUser(const char* username);
@@ -50,6 +52,8 @@
     virtual int getType() const { return secTypePlain; };
     virtual const char* getUserName() const { return username.buf; }
 
+    virtual ~SSecurityPlain() { }
+
   private:
     PasswordValidator* valid;
     unsigned int ulen, plen, state;
diff --git a/common/rfb/SSecurityVncAuth.h b/common/rfb/SSecurityVncAuth.h
index e9f379b..a1d1747 100644
--- a/common/rfb/SSecurityVncAuth.h
+++ b/common/rfb/SSecurityVncAuth.h
@@ -37,6 +37,8 @@
     // getVncAuthPasswd() fills buffer of given password and readOnlyPassword.
     // If there was no read only password in the file, readOnlyPassword buffer is null.
     virtual void getVncAuthPasswd(PlainPasswd *password, PlainPasswd *readOnlyPassword)=0;
+
+    virtual ~VncAuthPasswdGetter() { }
   };
 
   class VncAuthPasswdParameter : public VncAuthPasswdGetter, BinaryParameter {
diff --git a/common/rfb/Timer.h b/common/rfb/Timer.h
index e295b82..78687d1 100644
--- a/common/rfb/Timer.h
+++ b/common/rfb/Timer.h
@@ -49,6 +49,8 @@
       //   appropriate interval.
       //   If the handler returns false then the Timer is cancelled.
       virtual bool handleTimeout(Timer* t) = 0;
+
+      virtual ~Callback() {}
     };
 
     // checkTimeouts()
diff --git a/common/rfb/UserPasswdGetter.h b/common/rfb/UserPasswdGetter.h
index 18b0bae..aa72c1d 100644
--- a/common/rfb/UserPasswdGetter.h
+++ b/common/rfb/UserPasswdGetter.h
@@ -25,6 +25,8 @@
     // case no user name will be retrieved.  The caller MUST delete [] the
     // result(s).
     virtual void getUserPasswd(char** user, char** password)=0;
+
+    virtual ~UserPasswdGetter() {}
   };
 }
 #endif