diff --git a/app/x11.go b/app/x11.go
index b1a9061..8f77ae2 100644
--- a/app/x11.go
+++ b/app/x11.go
@@ -78,7 +78,7 @@
 func onResize(w, h int) {
 	// TODO(nigeltao): don't assume 72 DPI. DisplayWidth and DisplayWidthMM
 	// is probably the best place to start looking.
-	pixelsPerPt := 1
+	pixelsPerPt := float32(1)
 	eventsIn <- config.Event{
 		WidthPx:     w,
 		HeightPx:    h,