diff --git a/src/functions/arrow.js b/src/functions/arrow.js
index b96e97c1..145f19f2 100644
--- a/src/functions/arrow.js
+++ b/src/functions/arrow.js
@@ -9,6 +9,14 @@ import * as mml from "../buildMathML";
 
 import type {ParseNode} from "../parseNode";
 
+// Helper function
+const paddedNode = group => {
+    const node = new mathMLTree.MathNode("mpadded", group ? [group] : []);
+    node.setAttribute("width", "+0.6em");
+    node.setAttribute("lspace", "0.3em");
+    return node;
+};
+
 // Stretchy arrows with an optional argument
 defineFunction({
     type: "xArrow",
@@ -105,12 +113,11 @@ defineFunction({
     mathmlBuilder(group, options) {
         const arrowNode = stretchy.mathMLnode(group.label);
         let node;
-        let lowerNode;
 
         if (group.body) {
-            const upperNode = mml.buildGroup(group.body, options);
+            const upperNode = paddedNode(mml.buildGroup(group.body, options));
             if (group.below) {
-                lowerNode = mml.buildGroup(group.below, options);
+                const lowerNode = paddedNode(mml.buildGroup(group.below, options));
                 node = new mathMLTree.MathNode(
                     "munderover", [arrowNode, lowerNode, upperNode]
                 );
@@ -118,10 +125,13 @@ defineFunction({
                 node = new mathMLTree.MathNode("mover", [arrowNode, upperNode]);
             }
         } else if (group.below) {
-            lowerNode = mml.buildGroup(group.below, options);
+            const lowerNode = paddedNode(mml.buildGroup(group.below, options));
             node = new mathMLTree.MathNode("munder", [arrowNode, lowerNode]);
         } else {
-            node = new mathMLTree.MathNode("mover", [arrowNode]);
+            // This should never happen.
+            // Parser.js throws an error if there is no argument.
+            node = paddedNode();
+            node = new mathMLTree.MathNode("mover", [arrowNode, node]);
         }
         return node;
     },