diff --git a/lapce-data/src/config.rs b/lapce-data/src/config.rs
index 9b00ed7c..cd4f7954 100644
--- a/lapce-data/src/config.rs
+++ b/lapce-data/src/config.rs
@@ -376,7 +376,7 @@ pub fn update_file(key: &str, value: toml::Value) -> Option<()> {
         let path = Self::settings_file()?;
         std::fs::write(&path, toml::to_string(&main_table).ok()?.as_bytes()).ok()?;
 
-        None
+        Some(())
     }
 
     pub fn set_theme(&mut self, theme: &str, preview: bool) -> Option<()> {
diff --git a/lapce-ui/src/tab.rs b/lapce-ui/src/tab.rs
index 48cb480e..b689b94e 100644
--- a/lapce-ui/src/tab.rs
+++ b/lapce-ui/src/tab.rs
@@ -532,7 +532,8 @@ fn event(
                     }
                     LapceUICommand::UpdateSettingsFile(key, value) => {
                         if let Ok(value) = toml::Value::deserialize(value) {
-                            Config::update_file(key, value);
+                            let update_result = Config::update_file(key, value);
+                            debug_assert!(update_result.is_some());
                         }
                     }
                     LapceUICommand::OpenFileDiff(path, history) => {