diff --git a/SocketIOClientSwift/WebSocket.swift b/SocketIOClientSwift/WebSocket.swift
index 810f1b4..2fdb8f2 100644
--- a/SocketIOClientSwift/WebSocket.swift
+++ b/SocketIOClientSwift/WebSocket.swift
@@ -495,7 +495,7 @@ public class WebSocket : NSObject, NSStreamDelegate {
                 dataLength = UInt64(bytes[0].bigEndian)
                 offset += sizeof(UInt16)
             }
-            if bufferLen < offset {
+            if bufferLen < offset || UInt64(bufferLen - offset) < dataLength {
                 fragBuffer = NSData(bytes: buffer, length: bufferLen)
                 return
             }