diff --git a/internal/api/index.go b/internal/api/index.go
index 3c23eeb45..acc6838f9 100644
--- a/internal/api/index.go
+++ b/internal/api/index.go
@@ -38,7 +38,7 @@ func StartIndexing(router *gin.RouterGroup, conf *config.Config) {
 
 		indOpt := photoprism.IndexOptions{
 			Rescan:  f.Rescan,
-			Convert: f.Convert && !conf.ReadOnly(),
+			Convert: f.Convert && (!conf.ReadOnly() || filepath.IsAbs(conf.SidecarPath())),
 			Path:    filepath.Clean(f.Path),
 		}
 
diff --git a/internal/commands/index.go b/internal/commands/index.go
index 58bdc5659..78da7ba47 100644
--- a/internal/commands/index.go
+++ b/internal/commands/index.go
@@ -65,7 +65,7 @@ func indexAction(ctx *cli.Context) error {
 	indOpt := photoprism.IndexOptions{
 		Path:    subPath,
 		Rescan:  ctx.Bool("all"),
-		Convert: conf.Settings().Index.Convert && !conf.ReadOnly(),
+		Convert: conf.Settings().Index.Convert && (!conf.ReadOnly() || filepath.IsAbs(conf.SidecarPath())),
 	}
 
 	indexed := ind.Start(indOpt)