diff --git a/cmd/bitrot-streaming.go b/cmd/bitrot-streaming.go
index d707c70e2..7c1a313b7 100644
--- a/cmd/bitrot-streaming.go
+++ b/cmd/bitrot-streaming.go
@@ -20,6 +20,7 @@ package cmd
 import (
 	"bytes"
 	"context"
+	"errors"
 	"hash"
 	"io"
 	"sync"
@@ -37,12 +38,22 @@ type streamingBitrotWriter struct {
 	shardSize    int64
 	canClose     *sync.WaitGroup
 	byteBuf      []byte
+	finished     bool
 }
 
 func (b *streamingBitrotWriter) Write(p []byte) (int, error) {
 	if len(p) == 0 {
 		return 0, nil
 	}
+	if b.finished {
+		return 0, errors.New("bitrot write not allowed")
+	}
+	if int64(len(p)) > b.shardSize {
+		return 0, errors.New("unexpected bitrot buffer size")
+	}
+	if int64(len(p)) < b.shardSize {
+		b.finished = true
+	}
 	b.h.Reset()
 	b.h.Write(p)
 	hashBytes := b.h.Sum(nil)
diff --git a/cmd/erasure-multipart.go b/cmd/erasure-multipart.go
index f8a3bcdf4..a0d47849f 100644
--- a/cmd/erasure-multipart.go
+++ b/cmd/erasure-multipart.go
@@ -626,17 +626,13 @@ func (er erasureObjects) PutObjectPart(ctx context.Context, bucket, object, uplo
 	switch size := data.Size(); {
 	case size == 0:
 		buffer = make([]byte, 1) // Allocate at least a byte to reach EOF
-	case size == -1:
-		if size := data.ActualSize(); size > 0 && size < fi.Erasure.BlockSize {
-			// Account for padding and forced compression overhead and encryption.
-			buffer = make([]byte, data.ActualSize()+256+32+32, data.ActualSize()*2+512)
+	case size >= fi.Erasure.BlockSize || size == -1:
+		if int64(globalBytePoolCap.Load().Width()) < fi.Erasure.BlockSize {
+			buffer = make([]byte, fi.Erasure.BlockSize, 2*fi.Erasure.BlockSize)
 		} else {
 			buffer = globalBytePoolCap.Load().Get()
 			defer globalBytePoolCap.Load().Put(buffer)
 		}
-	case size >= fi.Erasure.BlockSize:
-		buffer = globalBytePoolCap.Load().Get()
-		defer globalBytePoolCap.Load().Put(buffer)
 	case size < fi.Erasure.BlockSize:
 		// No need to allocate fully fi.Erasure.BlockSize buffer if the incoming data is smaller.
 		buffer = make([]byte, size, 2*size+int64(fi.Erasure.ParityBlocks+fi.Erasure.DataBlocks-1))