diff --git a/src/backend/executor/execHHashagg.c b/src/backend/executor/execHHashagg.c
index ee2008717e03960d4514775dc1299c3d28f6e600..cf52f785cdd8e25e96c61bb22479b60082e1a38e 100644
--- a/src/backend/executor/execHHashagg.c
+++ b/src/backend/executor/execHHashagg.c
@@ -1626,11 +1626,13 @@ writeHashEntry(AggState *aggstate, BatchFileInfo *file_info,
 
 		if ((aggDataOffset + MAXALIGN(datum_size)) >= aggDataBufferSize)
 		{
-			aggDataBufferSize += BUFFER_INCREMENT_SIZE;
+			aggDataBufferSize += MAXALIGN(datum_size) >= BUFFER_INCREMENT_SIZE ?
+				MAXALIGN(datum_size) + BUFFER_INCREMENT_SIZE : BUFFER_INCREMENT_SIZE;
 			MemoryContext oldAggContext = MemoryContextSwitchTo(TopMemoryContext);
 			aggDataBuffer = repalloc(aggDataBuffer, aggDataBufferSize);
 			MemoryContextSwitchTo(oldAggContext);
 		}
+		Assert((aggDataOffset + MAXALIGN(datum_size)) <= aggDataBufferSize);
 		memcpy((aggDataBuffer + aggDataOffset), datum_value, datum_size);
 
 		aggDataOffset += MAXALIGN(datum_size);