diff --git a/index.bs b/index.bs
index 3e6f4a6e8..bcbc95e5b 100644
--- a/index.bs
+++ b/index.bs
@@ -2743,7 +2743,7 @@ PDF document represented as a Base64-encoded string.
         ? margin: browsingContext.PrintMarginParameters,
         ? orientation: ("portrait" / "landscape") .default "portrait",
         ? page: browsingContext.PrintPageParameters,
-        ? pageRanges: [*(js-uint / text)],
+        ? pageRanges: [*(js-uint / text .regex "^[0-9]+(?:-[0-9]+)?$" )],
         ? scale: (0.1..2.0) .default 1.0,
         ? shrinkToFit: bool .default true,
       }