diff --git a/internal/grid/debugmsg_string.go b/internal/grid/debugmsg_string.go
index 4c8676e39..a84f811b5 100644
--- a/internal/grid/debugmsg_string.go
+++ b/internal/grid/debugmsg_string.go
@@ -15,11 +15,12 @@ func _() {
 	_ = x[debugSetConnPingDuration-4]
 	_ = x[debugSetClientPingDuration-5]
 	_ = x[debugAddToDeadline-6]
+	_ = x[debugIsOutgoingClosed-7]
 }
 
-const _debugMsg_name = "debugShutdowndebugKillInbounddebugKillOutbounddebugWaitForExitdebugSetConnPingDurationdebugSetClientPingDurationdebugAddToDeadline"
+const _debugMsg_name = "debugShutdowndebugKillInbounddebugKillOutbounddebugWaitForExitdebugSetConnPingDurationdebugSetClientPingDurationdebugAddToDeadlinedebugIsOutgoingClosed"
 
-var _debugMsg_index = [...]uint8{0, 13, 29, 46, 62, 86, 112, 130}
+var _debugMsg_index = [...]uint8{0, 13, 29, 46, 62, 86, 112, 130, 151}
 
 func (i debugMsg) String() string {
 	if i < 0 || i >= debugMsg(len(_debugMsg_index)-1) {
diff --git a/internal/grid/muxclient.go b/internal/grid/muxclient.go
index 1b380a341..2078dc19a 100644
--- a/internal/grid/muxclient.go
+++ b/internal/grid/muxclient.go
@@ -91,7 +91,13 @@ func (m *muxClient) roundtrip(h HandlerID, req []byte) ([]byte, error) {
 		msg.Flags |= FlagSubroute
 	}
 	ch := make(chan Response, 1)
+	m.respMu.Lock()
+	if m.closed {
+		m.respMu.Unlock()
+		return nil, ErrDisconnected
+	}
 	m.respWait = ch
+	m.respMu.Unlock()
 	ctx := m.ctx
 
 	// Add deadline if none.
@@ -101,8 +107,8 @@ func (m *muxClient) roundtrip(h HandlerID, req []byte) ([]byte, error) {
 		ctx, cancel = context.WithTimeout(ctx, defaultSingleRequestTimeout)
 		defer cancel()
 	}
-	// Send... (no need for lock yet)
-	if err := m.sendLocked(msg); err != nil {
+	// Send request
+	if err := m.send(msg); err != nil {
 		return nil, err
 	}
 	if debugReqs {
@@ -215,7 +221,13 @@ func (m *muxClient) RequestStream(h HandlerID, payload []byte, requests chan []b
 		return nil, errors.New("RequestStream: responses channel is nil")
 	}
 	m.init = true
+	m.respMu.Lock()
+	if m.closed {
+		m.respMu.Unlock()
+		return nil, ErrDisconnected
+	}
 	m.respWait = responses // Route directly to output.
+	m.respMu.Unlock()
 
 	// Try to grab an initial block.
 	m.singleResp = false