diff --git a/api/layer/multipart_upload.go b/api/layer/multipart_upload.go
index d87af83..6ebfe4e 100644
--- a/api/layer/multipart_upload.go
+++ b/api/layer/multipart_upload.go
@@ -340,7 +340,7 @@ func (n *layer) CompleteMultipartUpload(ctx context.Context, p *CompleteMultipar
 	var completedPartsHeader strings.Builder
 	for i, part := range p.Parts {
 		partInfo := partsInfo[part.PartNumber]
-		if part.ETag != partInfo.ETag {
+		if partInfo == nil || part.ETag != partInfo.ETag {
 			return nil, nil, errors.GetAPIError(errors.ErrInvalidPart)
 		}
 		// for the last part we have no minimum size limit