diff --git a/sentinel-transport/sentinel-transport-simple-http/src/main/java/com/alibaba/csp/sentinel/transport/heartbeat/client/SimpleHttpClient.java b/sentinel-transport/sentinel-transport-simple-http/src/main/java/com/alibaba/csp/sentinel/transport/heartbeat/client/SimpleHttpClient.java
index 6befd46f38..5ec54e9fc1 100755
--- a/sentinel-transport/sentinel-transport-simple-http/src/main/java/com/alibaba/csp/sentinel/transport/heartbeat/client/SimpleHttpClient.java
+++ b/sentinel-transport/sentinel-transport-simple-http/src/main/java/com/alibaba/csp/sentinel/transport/heartbeat/client/SimpleHttpClient.java
@@ -156,6 +156,9 @@ private String getStatusLine(RequestMethod type, String requestPath) {
      * @return encoded request parameters, or empty string ("") if no parameters are provided
      */
     private String encodeRequestParams(Map<String, String> paramsMap, Charset charset) {
+        if (charset == null) {
+            throw new IllegalArgumentException("charset is not allowed to be null");
+        }
         if (paramsMap == null || paramsMap.isEmpty()) {
             return "";
         }