diff --git a/unpacked/jax/output/NativeMML/jax.js b/unpacked/jax/output/NativeMML/jax.js
index 63a3d5f75..dd87723f9 100644
--- a/unpacked/jax/output/NativeMML/jax.js
+++ b/unpacked/jax/output/NativeMML/jax.js
@@ -438,12 +438,12 @@
       var mW = math.offsetWidth  || math.scrollWidth,
           mH = math.offsetHeight || math.scrollHeight;
       var zW = span.offsetWidth, zH = span.offsetHeight;
-      if (nMML.widthBug) {
+      if (nMML.widthBug || span.style.width.match(/%/)) {
         //
         //  FF doesn't get width of <math> right, so get it from <mrow>
         //
         var W = span.firstChild.firstChild.scrollWidth;
-        if (W > zW) {zW = W; span.style.width = zW + "px"}
+        if (W > zW) {zW = W; span.parentNode.style.width = span.style.minWidth = zW + "px";}
       }
       if (this.msieIE8HeightBug) {span.style.position = ""}
       return {Y:-EVENT.getBBox(span.parentNode).h, mW:mW, mH:mH, zW:zW, zH:zH}