diff --git a/client.go b/client.go
index e2a4dd8..5debb87 100644
--- a/client.go
+++ b/client.go
@@ -632,18 +632,24 @@ func (c *Client) reader(t transport, disconnectCh chan struct{}) {
 func (c *Client) runHandlerSync(fn func()) {
 	waitCh := make(chan struct{})
 	c.mu.RLock()
-	c.cbQueue.push(func(delay time.Duration) {
-		defer close(waitCh)
-		fn()
-	})
+	if c.cbQueue != nil {
+		c.cbQueue.push(func(delay time.Duration) {
+			defer close(waitCh)
+			fn()
+		})
+	}
 	c.mu.RUnlock()
 	<-waitCh
 }
 
 func (c *Client) runHandlerAsync(fn func()) {
-	c.cbQueue.push(func(delay time.Duration) {
-		fn()
-	})
+	c.mu.RLock()
+	if c.cbQueue != nil {
+		c.cbQueue.push(func(delay time.Duration) {
+			fn()
+		})
+	}
+	c.mu.RUnlock()
 }
 
 func (c *Client) handle(reply *protocol.Reply) {