diff --git a/unpacked/jax/output/CommonHTML/jax.js b/unpacked/jax/output/CommonHTML/jax.js
index 5bab80d1b..c03332d72 100644
--- a/unpacked/jax/output/CommonHTML/jax.js
+++ b/unpacked/jax/output/CommonHTML/jax.js
@@ -1199,8 +1199,9 @@
     unEm: function (m) {
       return parseFloat(m);
     },
-    Px: function (m) {
+    Px: function (m,M) {
       m *= this.em;
+      if (M && m < M) m = M;
       if (Math.abs(m) < .1) return "0";
       return m.toFixed(1).replace(/\.0$/,"")+"px";
     },
@@ -2404,7 +2405,7 @@
             q = (u - nbox.d*nscale) - (a + t/2); if (q < p) u += (p - q);
             q = (a - t/2) - (dbox.h*dscale - v); if (q < p) v += (p - q);
             frac.style.verticalAlign = CHTML.Em(t/2-v);
-            num.style.borderBottom = CHTML.Px(t/nscale*nbox.scale)+" solid";
+            num.style.borderBottom = CHTML.Px(t/nscale*nbox.scale,1)+" solid";
             num.className += " MJXc-fpad";   nbox.L = nbox.R = .1;
             denom.className += " MJXc-fpad"; dbox.L = dbox.R = .1;
           }
@@ -2455,7 +2456,7 @@
         H = bbox.h + q + t;
         var x = this.CHTMLaddRoot(node,sbox,sbox.h+sbox.d-H);
         base.style.paddingTop = CHTML.Em(q); 
-        base.style.borderTop = CHTML.Px(T*bbox.scale)+" solid";
+        base.style.borderTop = CHTML.Px(T*bbox.scale,1)+" solid";
         sqrt.style.paddingTop = CHTML.Em(2*t-T);  // use wider line, but don't affect height
         bbox.h += q + 2*t;
         BBOX.combine(sbox,x,H-sbox.h);