diff --git a/Flow.Launcher.Plugin/IProgressBoxEx.cs b/Flow.Launcher.Plugin/IProgressBoxEx.cs
index 0b245411f..6468e3c83 100644
--- a/Flow.Launcher.Plugin/IProgressBoxEx.cs
+++ b/Flow.Launcher.Plugin/IProgressBoxEx.cs
@@ -6,7 +6,7 @@
 public interface IProgressBoxEx
 {
     /// <summary>
-    /// Show progress box
+    /// Show progress box. It should be called from the main ui thread.
     /// </summary>
     /// <param name="progress">
     /// Progress value. Should be between 0 and 100. When progress is 100, the progress box will be closed.
@@ -14,7 +14,7 @@ public interface IProgressBoxEx
     public void ReportProgress(double progress);
 
     /// <summary>
-    /// Close progress box.
+    /// Close progress box. It should be called from the main ui thread.
     /// </summary>
     public void Close();
 }