diff --git a/libmuscle/cpp/src/libmuscle/mcp/tcp_transport_server.cpp b/libmuscle/cpp/src/libmuscle/mcp/tcp_transport_server.cpp
index 98d52361..936305bf 100644
--- a/libmuscle/cpp/src/libmuscle/mcp/tcp_transport_server.cpp
+++ b/libmuscle/cpp/src/libmuscle/mcp/tcp_transport_server.cpp
@@ -284,7 +284,7 @@ class TcpTransportServerWorker {
 namespace libmuscle { namespace _MUSCLE_IMPL_NS { namespace mcp {
 
 TcpTransportServer::TcpTransportServer(RequestHandler & handler)
-    : TransportServer(handler)
+    : TransportServerBase(handler)
 {
     pipe(control_pipe_);
     thread_ = std::thread(server_thread_, this);
diff --git a/libmuscle/cpp/src/libmuscle/mcp/tcp_transport_server.hpp b/libmuscle/cpp/src/libmuscle/mcp/tcp_transport_server.hpp
index 933077c6..a3b5f690 100644
--- a/libmuscle/cpp/src/libmuscle/mcp/tcp_transport_server.hpp
+++ b/libmuscle/cpp/src/libmuscle/mcp/tcp_transport_server.hpp
@@ -16,7 +16,7 @@ namespace libmuscle { namespace _MUSCLE_IMPL_NS { namespace mcp {
 
 /** A server that accepts TCP connections.
  */
-class TcpTransportServer : public TransportServer {
+class TcpTransportServer : public TransportServerBase {
     public:
         /** Create a TcpTransportServer.
          *
diff --git a/libmuscle/cpp/src/libmuscle/mcp/transport_server.cpp b/libmuscle/cpp/src/libmuscle/mcp/transport_server.cpp
index 3337bad8..d5ff4575 100644
--- a/libmuscle/cpp/src/libmuscle/mcp/transport_server.cpp
+++ b/libmuscle/cpp/src/libmuscle/mcp/transport_server.cpp
@@ -6,7 +6,7 @@ namespace libmuscle { namespace _MUSCLE_IMPL_NS {namespace mcp {
 
 RequestHandler::~RequestHandler() {}
 
-TransportServer::TransportServer(RequestHandler & handler)
+TransportServerBase::TransportServerBase(RequestHandler & handler)
     : handler_(handler)
 {}
 
diff --git a/libmuscle/cpp/src/libmuscle/mcp/transport_server.hpp b/libmuscle/cpp/src/libmuscle/mcp/transport_server.hpp
index d3f7f052..d4118848 100644
--- a/libmuscle/cpp/src/libmuscle/mcp/transport_server.hpp
+++ b/libmuscle/cpp/src/libmuscle/mcp/transport_server.hpp
@@ -64,12 +64,6 @@ class RequestHandler {
  */
 class TransportServer {
     public:
-        /** Create a TransportServer.
-         *
-         * @param handler: A handler to handle requests
-         */
-        TransportServer(RequestHandler & handler);
-
         /** Destroy the Transport Server object
          */
         virtual ~TransportServer() = default;
@@ -86,6 +80,21 @@ class TransportServer {
          * then frees any other resources.
          */
         virtual void close() = 0;
+};
+
+
+/** Base class for TransportServers.
+ *
+ * They always have a handler, so this saves some typing. This is separate from the
+ * interface so that we can create a mock that doesn't have the reference.
+ */
+class TransportServerBase : public TransportServer {
+    public:
+        /** Create a TransportServerBase.
+         *
+         * @param handler: A handler to handle requests
+         */
+        TransportServerBase(RequestHandler & handler);
 
     protected:
         RequestHandler & handler_;