diff --git a/weixin4j-wxa/src/main/java/com/foxinmy/weixin4j/wxa/api/CustomMessageAdapters.java b/weixin4j-wxa/src/main/java/com/foxinmy/weixin4j/wxa/api/CustomMessageAdapters.java
index 421949d0..f5ac35be 100644
--- a/weixin4j-wxa/src/main/java/com/foxinmy/weixin4j/wxa/api/CustomMessageAdapters.java
+++ b/weixin4j-wxa/src/main/java/com/foxinmy/weixin4j/wxa/api/CustomMessageAdapters.java
@@ -21,7 +21,7 @@ final class CustomMessageAdapters {
 		final NotifyTuple tuple = customMessage.getTuple();
 		final String msgType = tuple.getMessageType();
 
-		final Map<String, Object> params = new HashMap<String, Object>();
+		final Map<String, Object> params = new HashMap<String, Object>(3);
 		params.put("touser", customMessage.getToUser());
 		params.put("msgtype", msgType);
 		params.put(msgType, customMessage.getTuple());