diff --git a/src/WebSocketConnection.ts b/src/WebSocketConnection.ts
index 1832e240..58c2b438 100644
--- a/src/WebSocketConnection.ts
+++ b/src/WebSocketConnection.ts
@@ -196,11 +196,7 @@ class WebSocketConnection {
 
     let stream = this.streamMap.get(streamId);
     if (stream == null) {
-      const messageType = remainder.at(0);
-      if (
-        messageType === StreamMessageType.Close ||
-        messageType === StreamMessageType.Error
-      ) {
+      if (remainder.at(0) !== StreamMessageType.Ack) {
         return;
       }
       stream = await WebSocketStream.createWebSocketStream({
diff --git a/tests/WebSocketStream.test.ts b/tests/WebSocketStream.test.ts
index 32a04035..655d35c1 100644
--- a/tests/WebSocketStream.test.ts
+++ b/tests/WebSocketStream.test.ts
@@ -53,10 +53,7 @@ jest.mock('@/WebSocketConnection', () => {
       let stream = instance.connectedConnection!.streamMap.get(streamId);
       if (stream == null) {
         const type = remainder.at(0);
-        if (
-          type === StreamMessageType.Close ||
-          type === StreamMessageType.Error
-        ) {
+        if (type !== StreamMessageType.Ack) {
           return;
         }
         stream = await WebSocketStream.createWebSocketStream({