diff --git a/src/Window.zig b/src/Window.zig
index fd74ba5..0be5341 100644
--- a/src/Window.zig
+++ b/src/Window.zig
@@ -215,6 +215,9 @@ pub fn create(alloc: std.mem.Allocator, app: *adw.Application) !*Window {
 
     const new_tab_button = gtk.Button.newFromIconName("tab-new-symbolic");
     new_tab_button.as(gtk.Widget).addCssClass("playpen-header-button");
+    // A MenuButton centers its inner button in the header bar, but a plain
+    // Button stretches to fill it; center this one too so the pair match.
+    new_tab_button.as(gtk.Widget).setValign(.center);
     new_tab_button.as(gtk.Widget).setTooltipText("New tab (Ctrl+Shift+T)");
     _ = gtk.Button.signals.clicked.connect(
         new_tab_button,