diff --git a/source/util/src/tlog.c b/source/util/src/tlog.c
index bd6c37a7b5..505ce61eca 100644
--- a/source/util/src/tlog.c
+++ b/source/util/src/tlog.c
@@ -573,6 +573,9 @@ void taosPrintSlowLog(const char *format, ...) {
   len += vsnprintf(buffer + len, LOG_MAX_LINE_DUMP_BUFFER_SIZE - 2 - len, format, argpointer);
   va_end(argpointer);
 
+  if (len < 0 || len > LOG_MAX_LINE_DUMP_BUFFER_SIZE - 2) {
+    len = LOG_MAX_LINE_DUMP_BUFFER_SIZE - 2;
+  }
   buffer[len++] = '\n';
   buffer[len] = 0;