diff --git a/tduck-wx-mp/src/main/java/com/tduck/cloud/wx/mp/handler/scan/ScanStrategyContext.java b/tduck-wx-mp/src/main/java/com/tduck/cloud/wx/mp/handler/scan/ScanStrategyContext.java
index 95cbed6..651aa8a 100644
--- a/tduck-wx-mp/src/main/java/com/tduck/cloud/wx/mp/handler/scan/ScanStrategyContext.java
+++ b/tduck-wx-mp/src/main/java/com/tduck/cloud/wx/mp/handler/scan/ScanStrategyContext.java
@@ -19,7 +19,7 @@ import java.util.Map;
 @RequiredArgsConstructor
 public class ScanStrategyContext {
 
-    private Map<String, ScanStrategy> scanStrategy;
+    private final Map<String, ScanStrategy> scanStrategy;
 
     private static String SCAN_STRATEGY_NAME = "ScanStrategy";