diff --git a/iris/src/default/render.rs b/iris/src/default/render.rs
index 970d44c..77829cc 100644
--- a/iris/src/default/render.rs
+++ b/iris/src/default/render.rs
@@ -115,7 +115,14 @@ impl UiRenderer {
             format: surface_format,
             width: size.width,
             height: size.height,
-            present_mode: PresentMode::AutoNoVsync,
+            // Vsync, because a UI toolkit aiming at battery life must not
+            // present frames a display will never show. AutoNoVsync accepts
+            // them as fast as the GPU will take them, so a redraw burst costs
+            // whatever the hardware can be made to do rather than one frame --
+            // and on this machine the GPU is the host's real one, reached
+            // through virtio-gpu, so that cost lands on somebody's desktop.
+            // AutoVsync picks Fifo, which every backend supports.
+            present_mode: PresentMode::AutoVsync,
             alpha_mode: surface_caps.alpha_modes[0],
             desired_maximum_frame_latency: 2,
             view_formats: vec![],