diff --git a/src/clientimpl.h b/src/clientimpl.h
index f6b40d5..5f4d4a7 100644
--- a/src/clientimpl.h
+++ b/src/clientimpl.h
@@ -81,7 +81,7 @@ struct RequestInfo {
     RequestInfo(uint32_t sid, uint32_t ioid, std::shared_ptr<OperationBase>& handle);
 };
 
-struct Connection : public ConnBase, public std::enable_shared_from_this<Connection> {
+struct Connection final : public ConnBase, public std::enable_shared_from_this<Connection> {
     const std::shared_ptr<ContextImpl> context;
 
     // While HoldOff, the time until re-connection
@@ -151,7 +151,7 @@ protected:
     static void tickEchoS(evutil_socket_t fd, short evt, void *raw);
 };
 
-struct ConnectImpl : public Connect
+struct ConnectImpl final : public Connect
 {
     const evbase loop;
     std::shared_ptr<Channel> chan;
@@ -223,7 +223,7 @@ struct Channel {
                                    const std::string& server);
 };
 
-struct Discovery : public OperationBase
+struct Discovery final : public OperationBase
 {
     const std::shared_ptr<ContextImpl> context;
     std::function<void(const Discovered &)> notify;
diff --git a/src/clientmon.cpp b/src/clientmon.cpp
index ca20f05..3262244 100644
--- a/src/clientmon.cpp
+++ b/src/clientmon.cpp
@@ -31,7 +31,7 @@ struct Entry {
 };
 }
 
-struct SubscriptionImpl : public OperationBase, public Subscription
+struct SubscriptionImpl final : public OperationBase, public Subscription
 {
     // for use in log messages, even after cancel()
     std::string channelName;
diff --git a/src/evhelper.cpp b/src/evhelper.cpp
index 237f953..103f0a0 100644
--- a/src/evhelper.cpp
+++ b/src/evhelper.cpp
@@ -107,7 +107,7 @@ struct ThreadEvent
     inline epicsEvent* operator->() { return get(); }
 };
 
-struct evbase::Pvt : public epicsThreadRunable
+struct evbase::Pvt final : public epicsThreadRunable
 {
     SockAttach attach;
 
diff --git a/src/serverconn.h b/src/serverconn.h
index 747be17..a068bb1 100644
--- a/src/serverconn.h
+++ b/src/serverconn.h
@@ -108,7 +108,7 @@ struct ServerChan
     void cleanup();
 };
 
-struct ServerConn : public ConnBase, public std::enable_shared_from_this<ServerConn>
+struct ServerConn final : public ConnBase, public std::enable_shared_from_this<ServerConn>
 {
     ServIface* const iface;
     const size_t tcp_tx_limit;
diff --git a/src/sharedpv.cpp b/src/sharedpv.cpp
index 08a6876..e55179d 100644
--- a/src/sharedpv.cpp
+++ b/src/sharedpv.cpp
@@ -467,7 +467,7 @@ Value SharedPV::fetch() const
     }
 }
 
-struct StaticSource::Impl : public Source
+struct StaticSource::Impl final : public Source
 {
     mutable RWLock lock;
 
diff --git a/src/udp_collector.cpp b/src/udp_collector.cpp
index 429b922..c693be8 100644
--- a/src/udp_collector.cpp
+++ b/src/udp_collector.cpp
@@ -31,8 +31,8 @@ namespace pvxs {namespace impl {
 DEFINE_LOGGER(logio, "pvxs.udp.io");
 DEFINE_LOGGER(logsetup, "pvxs.udp.setup");
 
-struct UDPCollector : public UDPManager::Search,
-                      public std::enable_shared_from_this<UDPCollector>
+struct UDPCollector final : public UDPManager::Search,
+                            public std::enable_shared_from_this<UDPCollector>
 {
     UDPManager::Pvt* const manager;
     SockAddr bind_addr; // address our socket is bound to
diff --git a/src/util.cpp b/src/util.cpp
index df9670e..9c6ce84 100644
--- a/src/util.cpp
+++ b/src/util.cpp
@@ -246,7 +246,7 @@ struct SocketPair {
 
 } // namespace
 
-struct SigInt::Pvt : public epicsThreadRunable {
+struct SigInt::Pvt final : private epicsThreadRunable {
     void (*prevINT)(int);
     void (*prevTERM)(int);
     const std::function<void()> handler;