diff --git a/src/common/src/tdataformat.c b/src/common/src/tdataformat.c
index db73905119e9ab6335d827f36ecf3bbb064d8f79..7ae34d532ca7ca52d3414a9d8f7366db15e046b8 100644
--- a/src/common/src/tdataformat.c
+++ b/src/common/src/tdataformat.c
@@ -462,8 +462,8 @@ int tdMergeDataCols(SDataCols *target, SDataCols *source, int rowsToMerge, int *
         }
       }
       target->numOfRows++;
-      (*pOffset)++;
     }
+    (*pOffset) += rowsToMerge;
   } else {
     pTarget = tdDupDataCols(target, true);
     if (pTarget == NULL) goto _err;