diff --git a/source/common/src/tdatablock.c b/source/common/src/tdatablock.c
index e8d5989e4d439be79a8816b5ca36f3e0c01eb7d9..f7b1196248eac45bcb1da2a8c60a573d3d4ab15c 100644
--- a/source/common/src/tdatablock.c
+++ b/source/common/src/tdatablock.c
@@ -277,7 +277,9 @@ int32_t colDataMergeCol(SColumnInfoData* pColumnInfoData, int32_t numOfRow1, int
       pColumnInfoData->varmeta.allocLen = len + oldLen;
     }
 
-    memcpy(pColumnInfoData->pData + oldLen, pSource->pData, len);
+    if (pColumnInfoData->pData && pSource->pData) { // TD-20382
+      memcpy(pColumnInfoData->pData + oldLen, pSource->pData, len);
+    }
     pColumnInfoData->varmeta.length = len + oldLen;
   } else {
     if (finalNumOfRows > (*capacity)) {