diff --git a/src/tsdb/src/tsdbRWHelper.c b/src/tsdb/src/tsdbRWHelper.c
index 170decc13ed5057aac05382fd7c0299f01191b7c..653379e03b1154cf95fab271286996f68fce170d 100644
--- a/src/tsdb/src/tsdbRWHelper.c
+++ b/src/tsdb/src/tsdbRWHelper.c
@@ -619,7 +619,11 @@ static int tsdbLoadBlockDataImpl(SRWHelper *pHelper, SCompBlock *pCompBlock, SDa
 
     if (pCompCol->colId == pDataCol->colId) {
       if (pCompBlock->algorithm == TWO_STAGE_COMP) {
-        pHelper->compBuffer = trealloc(pHelper->compBuffer, pCompCol->len + COMP_OVERFLOW_BYTES);
+        int zsize = pDataCol->bytes * pCompBlock->numOfPoints + COMP_OVERFLOW_BYTES;
+        if (pCompCol->type == TSDB_DATA_TYPE_BINARY || pCompCol->type == TSDB_DATA_TYPE_NCHAR) {
+          zsize += (sizeof(VarDataLenT) * pCompBlock->numOfPoints);
+        }
+        pHelper->compBuffer = trealloc(pHelper->compBuffer, zsize);
         if (pHelper->compBuffer == NULL) goto _err;
       }
       if (tsdbCheckAndDecodeColumnData(pDataCol, (char *)pCompData + tsize + pCompCol->offset, pCompCol->len,