diff --git a/libs/ardour/port.cc b/libs/ardour/port.cc
index 76552ea592..4f2020e392 100644
--- a/libs/ardour/port.cc
+++ b/libs/ardour/port.cc
@@ -219,7 +219,7 @@ Port::connected_to (std::string const & o) const
 		return false;
 	}
 
-	return port_engine.connected_to (_port_handle, AudioEngine::instance()->make_port_name_non_relative (o));
+	return port_engine.connected_to (_port_handle, AudioEngine::instance()->make_port_name_non_relative (o), true);
 }
 
 int
diff --git a/libs/ardour/port_engine_shared.cc b/libs/ardour/port_engine_shared.cc
index c4966240e7..6a5cbff369 100644
--- a/libs/ardour/port_engine_shared.cc
+++ b/libs/ardour/port_engine_shared.cc
@@ -748,12 +748,12 @@ PortEngineSharedImpl::connected (PortEngine::PortHandle port_handle, bool /* pro
 }
 
 bool
-PortEngineSharedImpl::connected_to (PortEngine::PortHandle src, const std::string& dst, bool /*process_callback_safe*/)
+PortEngineSharedImpl::connected_to (PortEngine::PortHandle src, const std::string& dst, bool process_callback_safe)
 {
 	BackendPortPtr src_port = boost::dynamic_pointer_cast<BackendPort> (src);
 	BackendPortPtr dst_port = find_port (dst);
 #ifndef NDEBUG
-	if (!valid_port (src_port) || !dst_port) {
+	if (!process_callback_safe && (!valid_port (src_port) || !dst_port)) {
 		PBD::error << string_compose (_("%1::connected_to: Invalid Port"), _instance_name) << endmsg;
 		return false;
 	}
diff --git a/libs/backends/alsa/alsa_audiobackend.cc b/libs/backends/alsa/alsa_audiobackend.cc
index 3c8fb1bc60..f979a1ecf3 100644
--- a/libs/backends/alsa/alsa_audiobackend.cc
+++ b/libs/backends/alsa/alsa_audiobackend.cc
@@ -1790,7 +1790,6 @@ AlsaAudioBackend::get_buffer (PortEngine::PortHandle port_handle, pframes_t nfra
 {
 	BackendPortPtr port = boost::dynamic_pointer_cast<BackendPort> (port_handle);
 	assert (port);
-	assert (valid_port (port));
 	return port->get_buffer (nframes);
 }
 
diff --git a/libs/backends/coreaudio/coreaudio_backend.cc b/libs/backends/coreaudio/coreaudio_backend.cc
index 9e9a119cdd..3afeb12a30 100644
--- a/libs/backends/coreaudio/coreaudio_backend.cc
+++ b/libs/backends/coreaudio/coreaudio_backend.cc
@@ -1218,7 +1218,6 @@ CoreAudioBackend::get_buffer (PortEngine::PortHandle port_handle, pframes_t nfra
 {
 	boost::shared_ptr<BackendPort> port = boost::dynamic_pointer_cast<BackendPort> (port_handle);
 	assert (port);
-	assert (valid_port (port));
 	if (!port || !valid_port (port)) return NULL; // XXX remove me
 	return port->get_buffer (nframes);
 }
diff --git a/libs/backends/portaudio/portaudio_backend.cc b/libs/backends/portaudio/portaudio_backend.cc
index 8298af53ff..5b3fc46bf4 100644
--- a/libs/backends/portaudio/portaudio_backend.cc
+++ b/libs/backends/portaudio/portaudio_backend.cc
@@ -1446,7 +1446,6 @@ PortAudioBackend::get_buffer (PortEngine::PortHandle port_handle, pframes_t nfra
 {
 	boost::shared_ptr<BackendPort> port = boost::dynamic_pointer_cast<BackendPort>(port_handle);
 	assert (port);
-	assert (valid_port (port));
 	if (!port || !valid_port (port)) return NULL; // XXX remove me
 	return port->get_buffer (nframes);
 }
diff --git a/libs/backends/pulseaudio/pulseaudio_backend.cc b/libs/backends/pulseaudio/pulseaudio_backend.cc
index 47fd73d939..8c4f08d224 100644
--- a/libs/backends/pulseaudio/pulseaudio_backend.cc
+++ b/libs/backends/pulseaudio/pulseaudio_backend.cc
@@ -981,7 +981,6 @@ PulseAudioBackend::get_buffer (PortEngine::PortHandle port_handle, pframes_t nfr
 	BackendPortPtr port = boost::dynamic_pointer_cast<BackendPort> (port_handle);
 
 	assert (port);
-	assert (valid_port (port));
 
 	return port->get_buffer (nframes);
 }