diff --git a/butterflow-ui/OptionsConfiguration.cs b/butterflow-ui/OptionsConfiguration.cs
index 5f8dc6a..8e24f89 100644
--- a/butterflow-ui/OptionsConfiguration.cs
+++ b/butterflow-ui/OptionsConfiguration.cs
@@ -452,6 +452,8 @@ namespace butterflow_ui
 
             if (this.Subregions.Any())
             {
+                stringBuilder.Append("-s ");
+
                 foreach (var anon in this.Subregions.Select((sr, index) => new { Index = index, Subregion = sr }))
                 {
                     string format = "ss\\.fff";