diff --git a/extern/sector-storage/fsutil/filesize_unix.go b/extern/sector-storage/fsutil/filesize_unix.go
index e5d220764..aadf93acc 100644
--- a/extern/sector-storage/fsutil/filesize_unix.go
+++ b/extern/sector-storage/fsutil/filesize_unix.go
@@ -3,6 +3,7 @@ package fsutil
 import (
 	"os"
 	"path/filepath"
+	"syscall"
 
 	"golang.org/x/xerrors"
 )
@@ -12,6 +13,7 @@ type SizeInfo struct {
 }
 
 // FileSize returns bytes used by a file or directory on disk
+// NOTE: We care about the allocated bytes, not file or directory size
 func FileSize(path string) (SizeInfo, error) {
 	var size int64
 	err := filepath.Walk(path, func(_ string, info os.FileInfo, err error) error {
@@ -19,7 +21,11 @@ func FileSize(path string) (SizeInfo, error) {
 			return err
 		}
 		if !info.IsDir() {
-			size += info.Size()
+			stat := info.Sys().(*syscall.Stat_t)
+
+			// NOTE: stat.Blocks is in 512B blocks, NOT in stat.Blksize		return SizeInfo{size}, nil
+			//  See https://www.gnu.org/software/libc/manual/html_node/Attribute-Meanings.html
+			size += int64(stat.Blocks) * 512 // nolint NOTE: int64 cast is needed on osx
 		}
 		return err
 	})