diff --git a/unpacked/extensions/TeX/AMSmath.js b/unpacked/extensions/TeX/AMSmath.js
index d2a0a380d..4615be6de 100644
--- a/unpacked/extensions/TeX/AMSmath.js
+++ b/unpacked/extensions/TeX/AMSmath.js
@@ -256,9 +256,14 @@ MathJax.Hub.Register.StartupHook("TeX Jax Ready",function () {
       if (thick !== "") {frac.linethickness = thick}
       if (left || right) {
         var mrow = MML.mrow();
-        if (left) {mrow.Append(MML.mo(left))}
+        mrow.open = left; mrow.close = right;
+        if (left) {
+          mrow.Append(MML.mo(left).With({fence: "true"}));
+        }
         mrow.Append(frac);
-        if (right) {mrow.Append(MML.mo(right))}
+        if (right) {
+          mrow.Append(MML.mo(right).With({fence: "true"}));
+        }
         frac = mrow;
       }
       if (style !== "") {
diff --git a/unpacked/jax/input/MathML/jax.js b/unpacked/jax/input/MathML/jax.js
index 1270eefb7..4fb758992 100644
--- a/unpacked/jax/input/MathML/jax.js
+++ b/unpacked/jax/input/MathML/jax.js
@@ -1,3 +1,5 @@
+/* -*- Mode: Javascript; indent-tabs-mode:nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
 /*************************************************************
  *
  *  MathJax/jax/input/MathML/jax.js
@@ -158,6 +160,14 @@
             {mml.Append.apply(mml,cmml.data); cmml.data = []}
         }
       }
+      if (mml.type === "mrow" && mml.data.length >= 2) {
+        var first = mml.data[0], last = mml.data[mml.data.length-1];
+        if (first.type === "mo" && first.fence &&
+            last.type === "mo" && last.fence) {
+          mml.open = first.data[0].data[0];
+          mml.close = last.data[0].data[0];
+        }
+      }
     },
     
     //
diff --git a/unpacked/jax/input/TeX/jax.js b/unpacked/jax/input/TeX/jax.js
index 5a6004435..b6cd72018 100644
--- a/unpacked/jax/input/TeX/jax.js
+++ b/unpacked/jax/input/TeX/jax.js
@@ -178,9 +178,14 @@
           mml.texClass = MML.TEXCLASS.INNER;
           mml.texWithDelims = true;
           var mrow = MML.mrow();
-          if (this.open) {mrow.Append(MML.mo(this.open))}
+          mrow.open = this.open; mrow.close = this.close;
+          if (this.open) {
+            mrow.Append(MML.mo(this.open).With({fence: "true"}));
+          }
           mrow.Append(mml);
-          if (this.close) {mrow.Append(MML.mo(this.close))}
+          if (this.close) {
+            mrow.Append(MML.mo(this.close).With({fence: "true"}));
+          }
           mml = mrow;
         }
         return [STACKITEM.mml(mml), item];
@@ -196,9 +201,16 @@
     checkItem: function (item) {
       if (item.type === "right") {
         var mml = MML.mrow();
-        if (this.delim) {mml.Append(MML.mo(this.delim))}
-        mml.Append(this.data.length === 1 ? this.data[0] : this.data);
-        if (item.delim) {mml.Append(MML.mo(item.delim))}
+        mml.open = this.delim; mml.close = item.delim;
+        if (this.delim) {
+          mml.Append(MML.mo(this.delim).With({fence: "true"}));
+        }
+        for (var i in this.data) {
+          mml.Append(this.data[i]);
+        }
+        if (item.delim) {
+          mml.Append(MML.mo(item.delim).With({fence: "true"}));
+        }
         return STACKITEM.mml(mml);
       }
       return this.SUPER(arguments).checkItem.call(this,item);
@@ -277,9 +289,14 @@
         }
         if (this.open || this.close) {
           var mrow = MML.mrow();
-          if (this.open) {mrow.Append(MML.mo(this.open))}
+          mrow.open = this.open; mrow.close = this.close;
+          if (this.open) {
+            mrow.Append(MML.mo(this.open).With({fence: "true"}))
+          }
           mrow.Append(mml);
-          if (this.close) {mrow.Append(MML.mo(this.close))}
+          if (this.close) {
+            mrow.Append(MML.mo(this.close).With({fence: "true"}))
+          }
           mml = mrow;
         }
         mml = STACKITEM.mml(mml);
diff --git a/unpacked/jax/output/NativeMML/jax.js b/unpacked/jax/output/NativeMML/jax.js
index e47e45304..5ed69d2da 100644
--- a/unpacked/jax/output/NativeMML/jax.js
+++ b/unpacked/jax/output/NativeMML/jax.js
@@ -1,3 +1,5 @@
+/* -*- Mode: Javascript; indent-tabs-mode:nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
 /*************************************************************
  *
  *  MathJax/jax/output/NativeMML/jax.js
@@ -467,7 +469,28 @@
 	    if (this.data[i]) {this.data[i].toNativeMML(parent)}
 	      else {parent.appendChild(this.NativeMMLelement("mrow"))}
 	  }
-	} else {
+	} else if (nMML.stretchyMoBug && (this.open || this.close)) {
+          // This element contains opening and/or closing fences. Opera is not
+          // able to stretch <mo> operators, so let's use an <mfenced> element
+          // instead.
+          var mfenced = this.NativeMMLelement("mfenced");
+          this.NativeMMLattributes(mfenced);
+          var i = 0, m = this.data.length;
+          if (this.open) { mfenced.setAttribute("open", this.open); i++; }
+          if (this.close) { mfenced.setAttribute("close", this.close); m--; }
+          var tag = mfenced;
+          if (m - i + 1 > 1) {
+            // If there are several children, put them in an <mrow>
+            tag = this.NativeMMLelement("mrow");
+	    parent.appendChild(mfenced);
+            parent = mfenced;
+          }
+          for (; i < m; i++) {
+	    if (this.data[i]) {this.data[i].toNativeMML(tag)}
+	    else {tag.appendChild(this.NativeMMLelement("mrow"))}
+	  }
+	  parent.appendChild(tag);
+        } else {
 	  this.SUPER(arguments).toNativeMML.call(this,parent);
 	}
       }
@@ -619,6 +642,95 @@
       }
     });
 
+    MML.mfenced.Augment({
+      toNativeMML: function (parent) {
+        if (!nMML.mfencedBug) {
+	  this.SUPER(arguments).toNativeMML.call(this,parent);
+          return;
+        }
+
+        // Some browsers do not handle <mfenced> very well. The MathML spec
+        // suggests this equivalent construction instead, so let's use it:
+        // <mrow> open, child1, sep1, child2, ... sep(N-1), childN, close</mrow>
+        // Opera is a bit special: it does not support stretchy <mo>, does not
+        // parse mfenced@open/mfenced@close very well, does not support
+        // mfenced@separators and only displays the first child of the <mfenced>
+        // element... For this browser, we will use this construction:
+        // <mfenced open="open" close="close">
+        //   <mrow>child1, sep1, child2, sep2, ..., sep(N-1), childN</mrow>
+        // </mfenced>
+        var isOpera = HUB.Browser.isOpera;
+
+        // parse the open, close and separators attributes.
+        var values = this.getValues("open","close","separators");
+        values.open = values.open.trim();
+        values.close = values.close.trim();
+        values.separators = values.separators.replace(/\s+/g,"").split("");
+        if (values.separators.length == 0) {
+          // No separators specified, do not use separators at all.
+          values.separators = null;
+        } else if (values.separators.length < this.data.length-1) {
+          // There are not enough separators, repeat the last one.
+          for (var s = values.separators[values.separators.length-1],
+               i = this.data.length-1-values.separators.length; i > 0; i--) {
+            values.separators.push(s)
+          }
+        }
+
+        // create an <mrow> container and attach the attributes of the
+        // <mfenced> element to it. Note: removeAttribute does not raise any
+        // exception when the attributes is absent.
+        var tag = this.NativeMMLelement(isOpera ? this.type : "mrow");
+        this.NativeMMLattributes(tag);
+        tag.removeAttribute("separators");
+        if (isOpera) {
+          tag.setAttribute("open", values.open);
+          tag.setAttribute("close", values.close);
+          if (this.data.length > 1) {
+            parent.appendChild(tag);
+            parent = tag;
+            tag = this.NativeMMLelement("mrow");
+          }
+        } else {
+          tag.removeAttribute("open");
+          tag.removeAttribute("close");
+        }
+
+        if (!isOpera) {
+          // append the opening fence
+          var operator = this.NativeMMLelement("mo");
+          operator.setAttribute("fence", "true");
+          operator.textContent = values.open;
+          tag.appendChild(operator);
+        }
+
+        // append the content of the <mfenced>
+        for (var i = 0, m = this.data.length; i < m; i++) {
+          if (values.separators && i > 0) {
+            var operator = this.NativeMMLelement("mo");
+            operator.setAttribute("separator", "true");
+            operator.textContent = values.separators[i-1];
+            tag.appendChild(operator);
+          }
+	  if (this.data[i]) {
+            this.data[i].toNativeMML(tag);
+          }
+	  else {tag.appendChild(this.NativeMMLelement("mrow"))}
+        }
+
+        if (!isOpera) {
+          // append the closing fence
+          var operator = this.NativeMMLelement("mo");
+          operator.setAttribute("fence", "true");
+          operator.textContent = values.close;
+          tag.appendChild(operator);
+        }
+
+        // finally, append the new element to the parent.
+        parent.appendChild(tag);
+      }
+    });
+
     MML.TeXAtom.Augment({
       //
       //  Convert TeXatom to an mrow
@@ -689,10 +801,19 @@
     },
     Opera: function (browser) {
       nMML.operaPositionBug = true;
+      nMML.stretchyMoBug = true;
+      nMML.mfencedBug = true;
     },
     Firefox: function (browser) {
       nMML.forceReflow = true;
       nMML.widthBug = true;
+      nMML.mfencedBug = true;
+    },
+    Safari: function (browser) {
+      nMML.mfencedBug = true;
+    },
+    Chrome: function (browser) {
+      nMML.mfencedBug = true;
     }
   });