diff --git a/rootfs/startup.sh b/rootfs/startup.sh
index 941520a..2241609 100755
--- a/rootfs/startup.sh
+++ b/rootfs/startup.sh
@@ -17,7 +17,7 @@ if [ -n "$OPENBOX_ARGS" ]; then
 fi
 
 if [ -n "$RESOLUTION" ]; then
-    sed -i "s/1024x768/$RESOLUTION/" /usr/local/bin/xvfb.sh
+    sed -i "s/.*exec /usr/bin/Xvfb :1 -screen.*/exec /usr/bin/Xvfb :1 -screen 0 $RESOLUTION/" /usr/local/bin/xvfb.sh
 fi
 
 USER=${USER:-root}