diff --git a/node/pkg/dal/api/controller.go b/node/pkg/dal/api/controller.go
index 7907ac54f..f2b9b5d0c 100644
--- a/node/pkg/dal/api/controller.go
+++ b/node/pkg/dal/api/controller.go
@@ -94,6 +94,8 @@ func (c *Controller) broadcastDataForSymbol(symbol string) {
 func (c *Controller) castSubmissionData(data *dalcommon.OutgoingSubmissionData, symbol *string) {
 	for conn := range c.clients {
 		if _, ok := c.clients[conn][*symbol]; ok {
+			c.mu.Lock()
+			defer c.mu.Unlock()
 			if err := conn.WriteJSON(*data); err != nil {
 				log.Error().Err(err).Msg("failed to write message")
 				delete(c.clients, conn)
diff --git a/node/pkg/dal/api/types.go b/node/pkg/dal/api/types.go
index 5a071aabd..862c3302a 100644
--- a/node/pkg/dal/api/types.go
+++ b/node/pkg/dal/api/types.go
@@ -1,6 +1,8 @@
 package api
 
 import (
+	"sync"
+
 	"bisonai.com/orakl/node/pkg/common/types"
 	"bisonai.com/orakl/node/pkg/dal/collector"
 	dalcommon "bisonai.com/orakl/node/pkg/dal/common"
@@ -20,4 +22,6 @@ type Controller struct {
 	register   chan *websocket.Conn
 	unregister chan *websocket.Conn
 	broadcast  map[string]chan dalcommon.OutgoingSubmissionData
+
+	mu sync.RWMutex
 }