diff --git a/main.ui b/main.ui
index 84b322c..ae46afb 100644
--- a/main.ui
+++ b/main.ui
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <object class="GtkApplicationWindow" id="app_window">
+  <object class="GtkApplicationWindow" id="app-window">
     <child>
       <object class="GtkBox">
         <property name="can-focus">False</property>
diff --git a/src/main.rs b/src/main.rs
index e08b309..2453b5a 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -14,7 +14,7 @@ fn main() {
 
 fn build_ui(app: &Application) {
     let builder = Builder::from_string(UI);
-    let app_window: ApplicationWindow = builder.object("app_window").unwrap();
+    let app_window: ApplicationWindow = builder.object("app-window").unwrap();
     app_window.set_application(Some(app));
     app_window.present();
 }