diff --git a/utils/test/c/tmqSim.c b/utils/test/c/tmqSim.c
index d81c70c65d..5eeb0aaa12 100644
--- a/utils/test/c/tmqSim.c
+++ b/utils/test/c/tmqSim.c
@@ -473,7 +473,7 @@ static char* shellFormatTimestamp(char* buf, int64_t val, int32_t precision) {
 
   struct tm ptm;
   if (taosLocalTime(&tt, &ptm) == NULL) {
-    sprintf(tt, "NaN");
+    sprintf(buf, "NaN");
     return buf;
   }
   size_t pos = strftime(buf, 35, "%Y-%m-%d %H:%M:%S", &ptm);