diff --git a/src/ParseNode.js b/src/ParseNode.js
index b865f29f..9e41460c 100644
--- a/src/ParseNode.js
+++ b/src/ParseNode.js
@@ -247,7 +247,7 @@ type ParseNodeTypes = {
     |},
     "raisebox": {|
         type: "raisebox",
-        dy: ParseNode<*>,
+        dy: ParseNode<"size">,
         body: ParseNode<*>,
         value: ParseNode<*>[],
     |},
diff --git a/src/buildHTML.js b/src/buildHTML.js
index f36915e0..805a4b04 100644
--- a/src/buildHTML.js
+++ b/src/buildHTML.js
@@ -12,7 +12,6 @@ import Style from "./Style";
 
 import buildCommon from "./buildCommon";
 import domTree from "./domTree";
-import { calculateSize } from "./units";
 import utils from "./utils";
 import stretchy from "./stretchy";
 import {spacings, tightSpacings} from "./spacingData";
@@ -570,25 +569,6 @@ export const groupTypes = {
 
         return makeSpan(["mrel", "x-arrow"], [vlist], options);
     },
-
-    raisebox(group, options) {
-        const body = groupTypes.sizing({value: {
-            value: [{
-                type: "text",
-                value: {
-                    body: group.value.value,
-                    font: "mathrm", // simulate \textrm
-                },
-            }],
-            size: 6,                // simulate \normalsize
-        }}, options);
-        const dy = calculateSize(group.value.dy.value, options);
-        return buildCommon.makeVList({
-            positionType: "shift",
-            positionData: -dy,
-            children: [{type: "elem", elem: body}],
-        }, options);
-    },
 };
 
 /**
diff --git a/src/buildMathML.js b/src/buildMathML.js
index 7621419b..b1502802 100644
--- a/src/buildMathML.js
+++ b/src/buildMathML.js
@@ -304,14 +304,6 @@ groupTypes.xArrow = function(group, options) {
     return node;
 };
 
-groupTypes.raisebox = function(group, options) {
-    const node = new mathMLTree.MathNode(
-        "mpadded", [buildGroup(group.value.body, options)]);
-    const dy = group.value.dy.value.number + group.value.dy.value.unit;
-    node.setAttribute("voffset", dy);
-    return node;
-};
-
 groupTypes.tag = function(group, options) {
     const table = new mathMLTree.MathNode("mtable", [
         new mathMLTree.MathNode("mlabeledtr", [
diff --git a/src/functions.js b/src/functions.js
index f431e3ed..84231662 100644
--- a/src/functions.js
+++ b/src/functions.js
@@ -2,7 +2,6 @@
 /** Include this to ensure that all functions are defined. */
 import {
     default as _defineFunction,
-    ordargument,
     _functions,
 } from "./defineFunction";
 
@@ -124,20 +123,7 @@ import "./functions/cr";
 import "./functions/environment";
 
 // Box manipulation
-defineFunction("raisebox", ["\\raisebox"], {
-    numArgs: 2,
-    argTypes: ["size", "text"],
-    allowedInText: true,
-}, function(context, args) {
-    const amount = args[0];
-    const body = args[1];
-    return {
-        type: "raisebox",
-        dy: amount,
-        body: body,
-        value: ordargument(body),
-    };
-});
+import "./functions/raisebox";
 
 import "./functions/verb";
 
diff --git a/src/functions/raisebox.js b/src/functions/raisebox.js
new file mode 100644
index 00000000..7182ed31
--- /dev/null
+++ b/src/functions/raisebox.js
@@ -0,0 +1,56 @@
+// @flow
+import defineFunction, {ordargument} from "../defineFunction";
+import buildCommon from "../buildCommon";
+import mathMLTree from "../mathMLTree";
+import {assertNodeType} from "../ParseNode";
+import {calculateSize} from "../units";
+
+import * as html from "../buildHTML";
+import * as mml from "../buildMathML";
+
+// Box manipulation
+defineFunction({
+    type: "raisebox",
+    names: ["\\raisebox"],
+    props: {
+        numArgs: 2,
+        argTypes: ["size", "text"],
+        allowedInText: true,
+    },
+    handler(context, args) {
+        const amount = assertNodeType(args[0], "size");
+        const body = args[1];
+        return {
+            type: "raisebox",
+            dy: amount,
+            body: body,
+            value: ordargument(body),
+        };
+    },
+    htmlBuilder(group, options) {
+        const body = html.groupTypes.sizing({value: {
+            value: [{
+                type: "text",
+                value: {
+                    body: group.value.value,
+                    font: "mathrm", // simulate \textrm
+                },
+            }],
+            size: 6,                // simulate \normalsize
+        }}, options);
+        const dy = calculateSize(group.value.dy.value, options);
+        return buildCommon.makeVList({
+            positionType: "shift",
+            positionData: -dy,
+            children: [{type: "elem", elem: body}],
+        }, options);
+    },
+    mathmlBuilder(group, options) {
+        const node = new mathMLTree.MathNode(
+            "mpadded", [mml.buildGroup(group.value.body, options)]);
+        const dy = group.value.dy.value.number + group.value.dy.value.unit;
+        node.setAttribute("voffset", dy);
+        return node;
+    },
+});
+