diff --git a/backend/mailru/api/m1.go b/backend/mailru/api/m1.go
index 91138d9a3..aba700a2f 100644
--- a/backend/mailru/api/m1.go
+++ b/backend/mailru/api/m1.go
@@ -117,7 +117,7 @@ type ListItem struct {
 	Name      string `json:"name"`
 	Home      string `json:"home"`
 	Size      int64  `json:"size"`
-	Mtime     int64  `json:"mtime,omitempty"`
+	Mtime     uint64 `json:"mtime,omitempty"`
 	Hash      string `json:"hash,omitempty"`
 	VirusScan string `json:"virus_scan,omitempty"`
 	Tree      string `json:"tree,omitempty"`
diff --git a/backend/mailru/mailru.go b/backend/mailru/mailru.go
index aeea7bc64..4d793933c 100644
--- a/backend/mailru/mailru.go
+++ b/backend/mailru/mailru.go
@@ -656,9 +656,14 @@ func (f *Fs) itemToDirEntry(ctx context.Context, item *api.ListItem) (entry fs.D
 	if err != nil {
 		return nil, -1, err
 	}
+	mTime := int64(item.Mtime)
+	if mTime < 0 {
+		fs.Debugf(f, "Fixing invalid timestamp %d on mailru file %q", mTime, remote)
+		mTime = 0
+	}
 	switch item.Kind {
 	case "folder":
-		dir := fs.NewDir(remote, time.Unix(item.Mtime, 0)).SetSize(item.Size)
+		dir := fs.NewDir(remote, time.Unix(mTime, 0)).SetSize(item.Size)
 		dirSize := item.Count.Files + item.Count.Folders
 		return dir, dirSize, nil
 	case "file":
@@ -672,7 +677,7 @@ func (f *Fs) itemToDirEntry(ctx context.Context, item *api.ListItem) (entry fs.D
 			hasMetaData: true,
 			size:        item.Size,
 			mrHash:      binHash,
-			modTime:     time.Unix(item.Mtime, 0),
+			modTime:     time.Unix(mTime, 0),
 		}
 		return file, -1, nil
 	default: