diff --git a/pkg/uploader/block/snapshot.go b/pkg/uploader/block/snapshot.go
index 595a80fd5..a0823de8c 100644
--- a/pkg/uploader/block/snapshot.go
+++ b/pkg/uploader/block/snapshot.go
@@ -110,10 +110,10 @@ func snapshotSource(
 
 	bitmap := cbt.NewBitmap(blockSize, uint64(source.size), cbtSource.Snapshot, parentBackup.changeID, parentBackup.volumeID)
 
-	err := cbt.SetBitmapOrFull(ctx, cbtService, bitmap)
+	err := cbt.SetBitmapOrFull(ctx, cbtService, bitmap, false)
 	if err != nil {
 		parentBackup.parentObject = ""
-		log.WithError(err).Warnf("Failed to create CBT with source %v, fallback to real full backup", cbtSource)
+		log.WithError(err).Warnf("Failed to create CBT with source %v", cbtSource)
 	}
 
 	snap, backupSize, err := u.Backup(source, parentBackup.parentObject, bitmap.Iterator(), uploaderCfg)
@@ -218,16 +218,12 @@ func Restore(ctx context.Context, blkUp Uploader, rep udmrepo.BackupRepo, snapsh
 	if incremental {
 		if snapshot.Tags == nil {
 			log.Warnf("No tag from snapshot %s, fallback to full restore", snapshotID)
-			incremental = false
 		} else if snapshot.Tags[uploader.CBTChangeIDTag] == "" {
 			log.Warnf("No ChangeID tag from snapshot %s, fallback to full restore", snapshotID)
-			incremental = false
 		} else if snapshot.Tags[uploader.CBTVolumeIDTag] == "" {
 			log.Warnf("No VolumeID tag from snapshot %s, fallback to full restore", snapshotID)
-			incremental = false
 		} else if snapshot.Tags[uploader.CBTVolumeIDTag] != cbtSource.VolumeID {
 			log.Warnf("VolumeID %s from snapshot %s is not expected as %s, fallback to full restore", snapshot.Tags[uploader.CBTVolumeIDTag], snapshotID, cbtSource.VolumeID)
-			incremental = false
 		} else {
 			volumeSnapshot = cbtSource.Snapshot
 			changeID = snapshot.Tags[uploader.CBTChangeIDTag]
@@ -237,8 +233,8 @@ func Restore(ctx context.Context, blkUp Uploader, rep udmrepo.BackupRepo, snapsh
 
 	bitmap := cbt.NewBitmap(blockSize, uint64(snapshot.TotalSize), volumeSnapshot, changeID, volumeID)
 	if incremental {
-		if err = cbt.SetBitmapOrFull(ctx, cbtService, bitmap); err != nil {
-			log.WithError(err).Warnf("Failed to create CBT with source %v, fallback to full restore", cbtSource)
+		if err = cbt.SetBitmapOrFull(ctx, cbtService, bitmap, true); err != nil {
+			log.WithError(err).Warnf("Failed to create CBT with source %v", cbtSource)
 		}
 	} else {
 		bitmap.SetFull()
diff --git a/pkg/uploader/cbt/bitmap.go b/pkg/uploader/cbt/bitmap.go
index f26cb22b7..f1b4b3c7d 100644
--- a/pkg/uploader/cbt/bitmap.go
+++ b/pkg/uploader/cbt/bitmap.go
@@ -36,6 +36,7 @@ type bitmapImpl struct {
 	snapshot     string
 	changeID     string
 	volumeID     string
+	cbtError     error
 }
 
 type bitmapIterator struct {
@@ -89,6 +90,14 @@ func (c *bitmapImpl) VolumeID() string {
 	return c.volumeID
 }
 
+func (c *bitmapImpl) SetError(err error) {
+	c.cbtError = err
+}
+
+func (c *bitmapImpl) Error() error {
+	return c.cbtError
+}
+
 func (c *bitmapImpl) Iterator() types.Iterator {
 	if c.bitmap == nil {
 		return nil
@@ -115,3 +124,7 @@ func (c *bitmapIterator) Count() uint64 {
 func (c *bitmapIterator) BlockSize() uint {
 	return c.blockSize
 }
+
+func (c *bitmapIterator) Error() error {
+	return c.cbtError
+}
diff --git a/pkg/uploader/cbt/set.go b/pkg/uploader/cbt/set.go
index 11361cf77..be039d0c7 100644
--- a/pkg/uploader/cbt/set.go
+++ b/pkg/uploader/cbt/set.go
@@ -26,36 +26,70 @@ import (
 )
 
 // SetBitmapOrFull translates the allocated/changed blocks from CBT service to the given bitmap or set the bitmap to full when error happens
-func SetBitmapOrFull(ctx context.Context, service cbtservice.Service, bitmap types.Bitmap) (err error) {
+func SetBitmapOrFull(ctx context.Context, service cbtservice.Service, bitmap types.Bitmap, incOnly bool) (ret error) {
+	setFull := false
+
 	defer func() {
-		if err != nil {
+		bitmap.SetError(ret)
+
+		if setFull {
 			bitmap.SetFull()
 		}
 	}()
 
 	if service == nil {
-		return errors.New("CBT service is absent")
+		setFull = true
+		return errors.New("CBT service is absent, fallback to real full")
 	}
 
 	if bitmap.Snapshot() == "" {
-		return errors.New("invalid snapshot")
+		setFull = true
+		return errors.New("invalid snapshot, fallback to real full")
 	}
 
-	if bitmap.ChangeID() == "" {
-		return errors.Wrapf(service.GetAllocatedBlocks(ctx, bitmap.Snapshot(), func(blocks []cbtservice.Range) error {
+	if incOnly && bitmap.ChangeID() == "" {
+		setFull = true
+		return errors.New("invalid changeID, fallback to real full")
+	}
+
+	var changedErr error
+	if bitmap.ChangeID() != "" {
+		err := service.GetChangedBlocks(ctx, bitmap.Snapshot(), bitmap.ChangeID(), func(blocks []cbtservice.Range) error {
 			for _, b := range blocks {
 				bitmap.Set(b.Offset, b.Length)
 			}
 
 			return nil
-		}), "error getting allocated blocks from CBT service")
+		})
+
+		if err == nil {
+			return nil
+		}
+
+		if incOnly {
+			setFull = true
+			return errors.Wrap(err, "error getting changed blocks from CBT service, fallback to real full")
+		}
+
+		changedErr = err
 	}
 
-	return errors.Wrapf(service.GetChangedBlocks(ctx, bitmap.Snapshot(), bitmap.ChangeID(), func(blocks []cbtservice.Range) error {
+	err := service.GetAllocatedBlocks(ctx, bitmap.Snapshot(), func(blocks []cbtservice.Range) error {
 		for _, b := range blocks {
 			bitmap.Set(b.Offset, b.Length)
 		}
 
 		return nil
-	}), "error getting changed blocks from CBT service")
+	})
+
+	if err != nil {
+		setFull = true
+		return errors.Wrap(err, "error getting allocated blocks from CBT service, fallback to real full")
+	}
+
+	if changedErr != nil {
+		return errors.Wrap(changedErr, "error getting changed blocks from CBT service, fallback to full")
+	}
+
+	return nil
 }
diff --git a/pkg/uploader/cbt/types/types.go b/pkg/uploader/cbt/types/types.go
index 9b13669b2..447c3f9f3 100644
--- a/pkg/uploader/cbt/types/types.go
+++ b/pkg/uploader/cbt/types/types.go
@@ -35,6 +35,12 @@ type Bitmap interface {
 
 	// Iterator returns the iterator for the CBT Bitmap
 	Iterator() Iterator
+
+	// SetError sets CBT error when preparing this bitmap
+	SetError(error)
+
+	// Error returns the CBT error when preparing this bitmap
+	Error() error
 }
 
 // Iterator defines the methods to iterate the CBT bitmap and query the associated information
@@ -56,4 +62,7 @@ type Iterator interface {
 
 	// Next returns the offset of the next set block and whether it comes to the end of the iteration
 	Next() (uint64, bool)
+
+	// Error returns the CBT error when preparing this bitmap
+	Error() error
 }