diff --git a/cmd/backoffice/fileserver.go b/cmd/backoffice/fileserver.go
index de8ca01..e0ae87e 100644
--- a/cmd/backoffice/fileserver.go
+++ b/cmd/backoffice/fileserver.go
@@ -41,12 +41,13 @@ func listCartFiles(dir string) ([]CartFileInfo, error) {
 			continue
 		}
 		name := e.Name()
-		var id int64
+		var idStr string
+		var id uint64
 		var parseErr error
 		parts := strings.Split(name, ".")
 		if len(parts) > 1 && parts[1] == "events" {
-			idStr := parts[0]
-			id, parseErr = strconv.ParseInt(idStr, 10, 64)
+			idStr = parts[0]
+			id, parseErr = strconv.ParseUint(idStr, 10, 64)
 		} else {
 			continue
 		}
@@ -59,7 +60,7 @@ func listCartFiles(dir string) ([]CartFileInfo, error) {
 			continue
 		}
 		out = append(out, CartFileInfo{
-			ID:       uint64(id),
+			ID:       idStr,
 			CartId:   cart.CartId(id),
 			Size:     info.Size(),
 			Modified: info.ModTime(),
diff --git a/cmd/backoffice/main.go b/cmd/backoffice/main.go
index f65d44a..1d0cfc1 100644
--- a/cmd/backoffice/main.go
+++ b/cmd/backoffice/main.go
@@ -17,7 +17,7 @@ import (
 )
 
 type CartFileInfo struct {
-	ID       uint64      `json:"id"`
+	ID       string      `json:"id"`
 	CartId   cart.CartId `json:"cartId"`
 	Size     int64       `json:"size"`
 	Modified time.Time   `json:"modified"`
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